Green’s Dictionary of Slang

(Polari) a word, thus v. to speak.

2019		P. Baker Fabulosa 294/1: lav a word.
2023		R. Milward Man-Eating Typewriter 5: Bona lavs.
2023		R. Milward Man-Eating Typewriter 70: I felt I was lavvying on a par with the gods.