What are the origins of "gender confirmation" surgery?

TLDR: What was the first use of the term "gender confirmation surgery"? Was it used before, after, or contemporaneously with the term "sex reassignment surgery"?

An NPR article today (2019-05-16) discusses the case of Adree Edmo, an inmate in Idaho who's suing the state to provide surgical intervention for treatment of gender dysphoria. Both the title of the article and URL use the phrase “sex reassignment” to refer to the surgery.

However, for most of the article, the phrase “gender confirmation” is used. After a quotation by Edmo’s lead attorney, the article states the following:

If Edmo wins her case, she’d become the first inmate to get gender confirmation surgery – also known as sex reassignment surgery – through court order, and it could open doors for others.

I hadn't heard the term before reading this article, and am wondering about its origin.

In another NPR article from June 2015 that also discusses this surgery, the term “sex reassignment” is used exclusively.

In the WPATH Standards of Care that discusses this surgery (and is linked to from today’s NPR article), the term “sex reassignment” is used exclusively.

Per Google Ngram Viewer, the term “gender confirmation surgery” doesn't appear in its collection of books.

Per Wikipedia(emphasis in original):

There are numerous other expressions that are used or have been used to refer to sexual reassignment surgery, including sex change operation, gender reassignment surgery, gender confirmation surgery, genital reconstruction surgery, gender-affirming surgery, and sex realignment surgery.

The American Society of Plastic Surgeons (ASPS) calls this procedure Gender Confirmation Surgery or GCS. Another term for SRS includes sex reconstruction surgery.

I was able to find a number of articles that do use the term "gender confirmation surgery", including a Huffington Post entry by a plastic surgeon that explains why he uses the term (as opposed to "sex reassignment").

As noted by @user240918, Merriam Webster indicates that the first use of this term was 1993; however, I've been unable to find this 1993 source. What was the first use of this term?

I want to emphasize that I have no interest in denigrating this term: I'm just curious about its origin.

The term most likely emerged as a research term. Here is the citation information and abstract for a 1988 article that describes sex reassignment as "gender confirmation":

Laub, D. R., et al. “Vaginoplasty for Gender Confirmation.” Clinics In Plastic Surgery, vol. 15, no. 3, July 1988, pp. 463–470.

Male-to-female surgery for properly diagnosed gender dysphoria, conducted as an interdisciplinary rehabilitation program, may be a valid endeavor in many cases. Successful surgical results have been obtained by those skilled in this type of surgery.

According to Google Scholar this text has been cited by 26 other texts. Some of these sources adopted the same terminology. For instance, here is another one from 1997:

Lenagham, R., Wilson, N, Lucas, C. E., Ledgerwood, A.M. "The role of rectosigmoid neocolporrhaphy." Surgery 122.4, 1997, 856-860.

Vaginoplasty for congenital vaginal atresia, a component of the Mayer-Rokitansky-Kuster syndrome, or for gender confirmation, may be achieved by several techniques.

At least some users of the phrase thought the usage of "gender confirmation" was preferable because they thought the gender of the patient was being discovered or realized and not changed. Here is a snippet from a 1989 book:

Marsh, J.L. Current Therapy in Plastic and Reconstructive Surgery: Trunk and extremities. Decker, 1989.

The surgeons change the body to fit what has been determined to be the real, or true, or best gender. As Edgerton has said: "We deal with gender confirmation surgery, not sex-change surgery.

The term had shown up in LGBT-facing media by the mid-1990s. Here's an excerpt from the magazine The Advocate from October 31, 1995:

I am certainly in favor of facilitating access to gender-confirmation surgery and other health care for adults with gender dysphoria ... It is clearly essential that this movement must include specific proposals to protect the right of transsexuals to have access to hormones and gender-confirmation surgery.

Most of the other search results from Google Books in the 1990s reflect surgical, specialist, or activist usage. From there, the usage must have reached more general audiences.