Let me explain in a chronological way.

In her 1989 book Spiritual Warfare, Sara Diamond  discussed how the Christian Right had been significantly influenced by Christian Reconstructionism and two of its major theologues: Gary North and the  late R.J. Rushdoony. The term “Dominion Theology” was already in use to describe Christian Reconstructionism.

Diamond, who would earn her PhD for her dissertation on  right-wing social movements in the United States, explained that "the  primary importance of the [Christian Reconstructionist] ideology is its role as  a catalyst for what is loosely called 'dominion theology.'"

According to  Diamond, "Largely through the impact of Rushdoony's and North's writings,  the concept that Christians are Biblically mandated to 'occupy' all secular  institutions has become the central  unifying ideology for the Christian Right." (Spiritual Warfare, p. 138, italics in  the original).

Fred Clarkson, the late Margaret Quigley, and I read Diamond’s  1989 Spiritual Warfare, and began  talking about what we should call Christian Right socio-political movements  influenced in some way by Christian Reconstructionism. Margaret and I had used  “Theocracy” for the broader concept while Fred used “Theonomy,” to describe  Dominion Theology. We agreed it was too confusing.

Diamond  began writing  articles on the Christian Right for the Humanist and Z Magazine. In a series of  articles and book chapters Diamond expanded on her thesis. She called  Reconstructionism "the most intellectually grounded, though esoteric,  brand of dominion theology," and observed that "promoters of  Reconstructionism see their role as ideological entrepreneurs committed to a  long-term struggle."

In 1992 author Bruce Barron warned of a growing "dominionist  impulse" among evangelicals in his book Heaven on Earth? The Social & Political Agendas of Dominion  Theology. Barron, with a Ph.D. in American religious history, is also an  advocate of Christian political participation, and has worked with conservative  Christian evangelicals and elected officials. Barron is smart, courteous, and  not someone you would debate without doing a whole boatload of homework.  Disrespect him at your own risk.

Barron was worried by the aggressive, intolerant, and  confrontational aspects of Dominion Theology; and was especially concerned that  these ideas had seeped into the broader Christian evangelical community.  Dominion Theology is not a version of Christianity with which Barron is  comfortable.

In his book, Barron looks at two theological currents:  Christian Reconstructionism and Kingdom Now, and explains that "Many  observers have grouped them together under the more encompassing rubric of  'dominion theology.'" Christian Reconstructionism evolved out of the writings  of R.J. Rushdoony; while Kingdom Now theology emerged from the ministry of Earl  Paulk.

"While differing from Reconstructionism in many ways,  Kingdom Now shares the belief that Christians have a mandate to take dominion  over every area of life," explains Barron. And it is just this tendency  that has spread through evangelical Protestantism, resulting in the emergence  of "various brands of 'dominionist' thinkers in contemporary American  evangelicalism," according to Barron.

I later met Barron when lecturing in Pennsylvania (I think it was Pennsylvania)  and we had a cordial conversation in which we agreed it made sense to reserve the term Dominion  Theology for the most hard-core theocrats. We also agreed that not every  evangelical was in the Christian Right and not everyone in the Christian Right  was a Dominionist. But keep in mind that back then some people were using the term "Dominionist" as synonymous with "Dominion Theology.

In December 1992 Margaret & I wrote “Theocracy and White  Supremacy: Behind the Culture War to  Restore Traditional Values,” for the Public  Eye Magazine.

Fred Clarkson and I had numerous and lengthy conversations  on this subject between 1992-1995.  We  tossed around several terms and ways to accurately, fairly, and respectfully  describe the tendency we could see in action inside the Christian Right.

In his thoughtful 1993 study "A Reformed Approach to  Economics: Christian Reconstructionism," Edd S. Noell explains the nuts  and bolts of how the Christian Reconstructionists view economic theory through  the lens of Biblical law. Noell is an Associate Professor of Economics at  Westmont College, and has done his homework. According to Noell:

The teachings of Christian Reconstructionism have  been increasingly influential in recent years for evangelicals advocating  social policy in various mainline denominations and independent churches. They  have also induced a fairly strong and at times quite critical reaction both  within and outside the Reformed community; among the sobriquets given to  Reconstructionists are “ triumphalists ” and “the liberation theologians of the  right.” (Bulletin, Association of Christian Economists, Spring, 1993,  pp. 6-20) http://www.gordon.edu/ace/pdf/NoellS93.pdf

In 1995 with Diamond’s permission I combined some of her  articles into a chapter in Eye’s Right!  Challenging the Right Wing Backlash. The title of the chapter was “The  Christian Right Seeks Dominion: On the Road to Political Power and Theocracy”

Diamond published Roads  to Dominion: Right-Wing Movements and  Political Power in the United States in 1995. It was a masterpiece of  sociological social movement theory.

Somewhere between 1989 and 1995 some of us started to use  the term Dominionism, especially after Roads  to Dominion came out.  It seemed that  for the Christian Right the influence of Dominion Theology had paved the path  for their “road to dominion.”

William Martin is the author of the 1996 tome With God on  Our Side, a companion volume to the PBS series of the same name (Martin and  I were both advisers to the PBS series of the same name). Martin is a  sociologist and professor of religion at Rice University, and he has been  critical of the way some critics of the Christian Right have tossed around the  terms "dominionism" and "theocracy." Martin has offered  some careful writing on the subject.

According to Martin:

It is difficult to assess the influence of  Reconstructionist thought with any accuracy. Because it is so genuinely  radical, most leaders of the Religious Right are careful to distance themselves  from it. At the same time, it clearly holds some appeal for many of them. One  undoubtedly spoke for others when he confessed, 'Though we hide their books  under the bed, we read them just the same.'

According to Martin, "several key leaders have  acknowledged an intellectual debt to the theonomists.” The late Christian Right  leaders Jerry Falwell and D. James Kennedy “endorsed Reconstructionist books"  for example, noted Martin. Before he died in 2001, the founder of Christian  Reconstuctionism, R. J. Rushdoony, appeared several times on Christian Right  televangelist programs such as Pat Robertson's 700 Club and the program hosted  by D. James Kennedy, writes Martin.

"Pat Robertson makes frequent use of 'dominion'  language" says Martin. Robertson’s book, The Secret Kingdom, “has often been cited for its theonomy  elements; and pluralists were made uncomfortable when, during his presidential  campaign, he said he 'would only bring Christians and Jews into the  government,' as well as when he later wrote, 'There will never be world peace  until God's house and God's people are given their rightful place of leadership  at the top of the world.' "

Martin also pointed out that Jay Grimstead, who led the  Coalition on Revival, “brought Reconstructionists together with more mainstream  evangelicals.” According to Martin, Grimstead explained “'I don't call myself  [a Reconstructionist],” but “A lot of us are coming to realize that the Bible  is God's standard of morality . . . in all points of history . . . and for all  societies, Christian and non-Christian alike. . . . It so happens that  Rushdoony, Bahnsen, and North understood that sooner.”

Then Grimstead added, “there are a lot of us floating around  in Christian leadership--James Kennedy is one of them--who don't go all the way  with the theonomy thing, but who want to rebuild America based on the Bible."

Fred Clarkson wrote Eternal  Hostility: The Struggle Between Theocracy and Democracy in 1997. Fred  continued writing about Christian Reconstructionism and Dominionism, including  an article in the Public Eye magazine: "The Rise of Dominionism: Remaking America as a Christian Nation" in 2005.

I have credited Diamond with popularizing the concept that  there was a dynamic involving Dominion Theology and the broader Christian  Right.  So Diamond popularized the idea  that seeking “dominion” was an important social movement dynamic inside the  Christian Right. 

So arguably Fred Clarkson and I developed the term  “Dominionism” in a series of conversations that stretched over several years.  Fred and I began to use the term "Dominionism" in speeches and interviews to describe the broader tendency as distinct from "Dominion Theology." It is possible  that Barron used it in print before we did.   Fred might know, but this is my version of reality. I expect Fred has a  different version.   The Rashomon Effect.  If we didn’t create the term Dominionism, Fred and I certainly have been the primary progressive activists to urge other writers to use it. But the scholarly concept was originated by Sara Diamond, who makes no  claims on crafting the terms “Dominion Theology” or “Dominionism.” So please stop calling her and asking for an interview. She prefers her privacy.

Let's choose our language carefully, but let's recognize  that terms such as "Dominionism" and "Theocracy," when used  cautiously and carefully, are appropriate when describing troubling tendencies  in the Christian Right.