Up to my retirement at the turn of the century, the P-3 community didn't regularly bestow callsigns on the pilots or "FO's." However, if someone did something significantly stupid, they definitely earned a nickname.
One of the JO's who was on my crew had the last name of Howell. When he checked into the squadron, this newbie NFO introduced himself by saying, "Hi, I'm LTJG ---- Howell, but you can call me "Thurston." Of course, he was referring to Thurston Howell the Third, the old, rich snob from "Gilligan's Island." And of course, we DIDN'T call him Thurston. No one picks their own nickname.
From then on, he was "Lovey" (Thurston's equally snobby old wife, Eunice Lovelle Wentworth Howell.) I ran into him again after I retired and became a Navy Civilian. He was an O-5...and was still being called "Lovey."
My nickname, Sweet Lou, came from the ballplayer, Lou Piniella. "Sweet Lou" Piniella's nickname was used facetiously as he had a very gruff demeanor. I was pretty laid back as a new O-4 but some of the JOs at my shore command just started calling me "Sweet Lou." A few months into my squadron Dept Hd tour, where my "Sweet Lou" nickname followed me, we got another O-4 onboard who happened to be the only other guy in the P-3 community with the same uncommon last name (Mosier). His demeanor was much more like Lou Piniella's so the JOs started calling him "Sour Lou," even though his first name was Jon. He hated that nickname, so of course it stuck.
