Verb Birds were warbling in the trees. He warbled his way through the song.
Word History
Etymology
Noun (1)
Middle English werble tune, from Old French (Picard dialect), from werbler to sing expressively, trill, of Germanic origin; akin to Middle Dutch wervelen to turn, Old High German wirbil whirlwind — more at whirl
Noun (2)
perhaps of Scandinavian origin; akin to obsolete Swedish varbulde boil, from var pus + bulde swelling