cavity n.

*keuə-, Proto-Indo-European root meaning "to swell," also "vault, hole."

It forms all or part of: accumulate; accumulation; cave; cavern; cavity; coeliac; church; codeine; coelacanth; coeliac; coelomate; concave; cumulate; cumulative; cumulus; enceinte; excavate; kirk; kymatology; Kyrie eleison.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit svayati "swells up, is strong;" Greek kyein "to swell," koilos "hollow, hollowed out, spacious, deep;" Latin cumulus "a heap, pile, mass, surplus;" Lithuanian šaunas "firm, solid, fit, capable;" Middle Irish cua "hollow;" Armenian soyl "cavity."

"to form cavities or bubbles (in a fluid)," 1892 (implied in cavitated), back-formation from cavitation or else formed from cavity + -ate (2) . Related: Cavitating.

"formation of bubbles in fluid," 1895, from cavity + -ation. Earlier as a medical term, "formation of cavities in the body" (1868).