Wordorigins.org

Cockpit seems a rather strange choice to denote the pilot’s compartment on an airplane, but once the semantic history of the word is known, all becomes clear.

Cockpit originally referred to a place for cock-fighting, literally a pit for fighting cocks. Thomas Churchyard writes in The Worthines of Wales (1587):

The Mountaynes stand...In roundnesse such as it a Cock pit were.