I had an aunt who was always called
Pat, even by her husband-her name was actually
Elsie. I don't know why, though I suppose someone must. As a sort of post-script-her niece was named after her--Patrica! always called
Patty, or really,
Paddy.
another addition-an uncle (same family) names
Edgar, was known as Tee-Tee. not by his friends though, they called him
Ed.