Lee Iacocca supposedly named the K-Cars after his daughter, Kathy.
Even better was when Iacocca tasked Carroll Shelby with the job of designing a car to compete with the Volkswagen Rabbit GTI. He insisted that it have a three letter name.
Shelby and his engineers worked at it, and Carroll presented Lee with the Dodge Omni GLH. “What does the ‘GLH’ stand for?” Iacocca asked.
“Goes Like Hell.”
Just about any car by Alfa Romeo and then there’s the Opel Omega. The linked Wiki-article also mentions a Oldsmobile Omega.
Scions first two models were the xA and the xB. When they made their third model they named it the tC because Volvo already used the xC nomenclature on their cross country vehicles. (Cross Country = XC)
Lotus 7.
Fiat Uno