the.com/airlock

means A sealed chamber with two doors that lets you pass between environments of different pressure—like a spacecraft and the void—without ever exposing one to the other.

from A transparent compound from English: 'air' bolted to 'lock,' the same 'lock' as in a canal lock, where boats rise and fall between water levels through gated chambers. The canal sense came first—a 'lock' as a controlled passage between two states—and the airlock simply borrowed the trick, swapping rising water for managed air. The word grew up alongside diving, mining, and pressurized engineering before space made it famous.