Met a Marine F-4 RIO some years ago whose call sign was 'Vahmit."
It was explained to me that for the first 50 missions over Viet Nam, he was airsick, hence the nickname. On on the 51st, that habit simply went away. The call sign didn't.
Ran into an F-4 pilot, similar vintage, USMC major, named George Stewart (or was it Stuart?) whose call sign was 'Smut.' If you ever asked him the name's origin, you'd only get a quiet smile and his standard response: "You're not cleared to know that."
Worked with a USAF A-10 pilot whose last name was Cates.
His call sign at the time I worked with him was "Defa"
He showed me a name tag from previous unit with "Forni" on it. That one's a bit too easy.