1580s, "a pit or enclosed space for fighting cocks," from cock (n.1) + pit (n.1). Used in nautical sense (1706) for midshipmen's compartment below decks; transferred to airplanes (1914) and to racing cars (1930s).

late 15c., "small boat," from Old French nacele "little boat, bark, skiff" (12c., Modern French nacelle), from Vulgar Latin *naucella, from Late Latin navicella "a little ship," diminutive of Latin navis "ship" (from PIE root *nau- "boat"). The original sense was soon obsolete. Modern meaning "gondola of an airship" is from 1901, a borrowing from French; extended to "cockpit of an aircraft" by 1914; later transferred to other similar housings and structures.

"testicles," early 14c., from plural of ball (n.1). See also ballocks. Meaning "courage, nerve" is from 1928. Balls to the wall, however, probably is from World War II Air Forces slang, from the ball that topped the aircraft throttle, thrust to the bulkhead of the cockpit to attain full speed.

Ball-busting "difficult" is recorded by 1944; ball-breaker "difficult job or problem" is by 1954. Ball-buster, disparaging for "dominant female, woman who destroys men's self-confidence" is from 1954; ball-breaker in this sense is by 1970 (of Bella Abzug).