The word turtle-dove has nothing to do with turtles in the slightest. It comes from Middle English turtildove, also spelled as turtilldove, turtledoue, and turtyldoue; that's composed out of turtur, the name of the genus, and the Middle English word for dove. Turtur traces to Latin, and that's it: the term is onomatopoeic for the bird's call. Dove traces to the Old English word dufe, which could also have a definition of "pigeon". Dufe comes from Proto-Germanic dubo, which in turn derives from the Proto-Indo-European reconstruction dewb, meaning "to move quickly" or "be obscure". Turtle-dove in the context of it being a verb meaning "to show affection" first originated in 1922. The hyphenated version of the word used to be much more popular, but now it's in second place in usage, behind turtledove and just ahead of turtle dove.
Adam Aleksic, a rising sophomore studying linguistics and government at Harvard University, has been described as the internet's sixth most famous etymologist. He also has disturbing interests in politics, vexillology, geography, board games, conlanging, and law.