My mom actually wanted to name me Penelope & call me Penny. Dad liked Wendy better, &, for whatever reason, he won. My middle name is a version of my Mom's middle name.
I've been told he liked the name Wendy because of the song like another PP mentioned, but I've also been told I was named after Wendy, Casper's friendly witch. When you ask either one of them now, they just say they liked the way Wendy sounded.
I grew up not really liking the name & thinking it sounded too much like all the other names ending in the "ee" sound of the decade - Becky, Debbie, Kelly, Lori, Stacy, etc.
I always wanted a more literary sounding name like Elizabeth. One day, however, I read where J. M. Barrie (the author of Peter Pan) was the one who actually first used the name. So now I really like my name!