Dex got it exactly right.
But let me add some other LL’s
Lyla Lumni (I’m butchering the spelling): an alien chick Superman fell in love with.
Lyla Ler-Ol (ditto): Superman went back to Krypton and went on a double-date with Jor-El and Laura with this Kryptonian actress
Lara Lar-Van (Lor-Van?), Superman’s mommy, with maiden name.
Linda Lee: Supergirl’s secret ID, before she was adopted.
Light Lass: (aKa: Lightning Lass)-Legion of Superheros member
Lightning Lord: Legion of Super-Villians member
Lena Thorul (aka Lena Luthor): Lex’s little sister…their parents changed their last name.
There’re others, but off the top of my head that’s the best I can do for now.
ResIpsaLoquitor: there’s a similar story with Superman. A future viewing-computer tells Superman that his life will be saved by “LL” today. A Green Kryptonite meteor just happens to fall near Superman. He thinks "A-HA! This is when my life will be saved by an “LL”. But none come. He uses his telescopic and x-ray vision to check out all the "LL"s he knows. They’re all busy (even Luthor and the Legion LLs…I don’t remember how he saw into the future).
Just as he’s about to pass out, a kid playing baseball goes to catch a ball and stumbles across Superman. The kid tosses the meteor in the (apparently lead-lined?!) sewers and Superman promptly recovers. He asks the kid his name, sure that it’ll be an LL. The kid tells Superman his name is (let’s say) Joe Smith. Superman’s shocked! The computer was wrong! Until the kid turns around and Superman realizes that the kid was playing for the Little League!
They don’t write 'em like that any more, dammit.