John Kelly in the Washington Post:
A reader asks: At Washington National Cathedral, on the wall of the stairwell leading down to the restrooms, there is a stone plaque that reads in large capital letters: "GITMO." What is its meaning?
— Shirley Cherkaksy, Alexandria
Kelly Replies: It means Guantanamo Bay, as in the U.S. Navy base on the southeast corner of Cuba. In 1965, the officers and men of the naval base donated the gray, rectangular stone to the cathedral, which was then under construction. The gift was in appreciation for a visit in July 1964 from the dean of the cathedral, the Rev. Francis B. Sayre Jr.
Sayre served as a Navy chaplain during World War II so he might have had a soft spot for sailors and Marines serving far from home. Of course, back then, Guantanamo Bay didn’t have the unfortunate associations it does now, and those five letters wouldn’t have seemed quite so jarring in that sacred setting.
And there is more on this story: John Kelly – Answer Man Leaves No Stone Unturned in Search for Cathedral Details – washingtonpost.com