The OED's earliest citation is for the noun lark, in in Lexicon Balatronicum: a dictionary of buckish slang, university wit, and pickpocket eloquence (1811):
Lark, a piece of merriment. People playing together jocosely.
Their etymology is:
Possibly it may represent the northern lake v.1 [To exert oneself, move quickly, leap, spring; hence, to fight. Obs.], as heard by sporting men from Yorkshire jockeys or grooms; the sound /læək/ , which is written lairk in Robinson's Whitby Glossary and in dialect books, would to a southern hearer more naturally suggest ‘lark’ than ‘lake’ as its equivalent in educated pronunciation. On the other hand, it is quite as likely that the word may have originated in some allusion to lark n.1 [the bird]; compare the similar use of skylark vb., which is found a few years earlier (1809).