What “LV” stands for?

[Kradan]

[Nukiemorph]

Still seems like code names come first, and noteworthy planets get actual names later.

[BigDaddyJohn]

Lovely Vibes.

[SiL]

Or Acheron.

Acheron is a nickname we don't hear in the movies. Its only name in the films is LV-426

[SM]

Can only guess it was to avoid confusion by giving it two names.  The script had a line from Van Leuwen telling Ripley "They call it Acheron now".  And I think the sign was also supposed to have 'Acheron' too.