the common European lark, 1680s, from sky, n. + lark, n.1. So called because it sings as it mounts toward the sky in flight.

"to frolic or play," 1809, originally nautical, in reference to "wanton play about the rigging, and tops," probably from skylark, n., influenced by (or from) lark, n.2. Related: Skylarked; skylarking.