I wanted to leave my given first initial intact, but there were no female equivalents of my first name (Gregory). I didn't want a name that had an obvious male equivalent, (Michelle, Paula, Briana...) as I didn't want people to falsely assume my original name. I also didn't want one that was unisex (Leslie, Dana, Alex). I could also eliminate names of people near and dear to me, and people I couldn't stand to be around. My mother would have named me Juliana if I was FAAB, but my much younger sister got that one. I also like anagrams.
All roads seemed to lead to Gillian. An anglicized version of Juliana, starts with "G", all letters originating from my birth name, and every Jill I ever met was awesome. Love it. The first name I tried on was Ginger, for the obvious anagram (In Greg), but it so didn't fit.
My middle name is Elizabeth. Classic, regal, elegant. It could have been Victoria as well, but Elizabeth won out. And my wife is 100% Brit.
I took her last name as well. She stuck with me, and that means the world. She is my rock to the very end.
And don't even think about calling me Jack.