Is it ensure, insure, or assure?
1821, from buoyant + -ance.
1713, from buoyant + -cy. Figurative sense (of spirits, etc.) is from 1819.
The force that causes objects to float. According to the principle of Archimedes, when a solid is placed in a fluid (a liquid or a gas), it is subject to an upward force equal in magnitude to the weight of the fluid it has displaced.