Where does “jailer” come from?

Jailer comes from Old French jaioleur, derived from Old French jaiole, a word of uncertain ultimate origin.

jailer (English): One who enforces confinement in a jail or prison

Definitions

Step	Language	Word	Meaning
1	Middle English	gayoler	—
2	Middle English	gayole	—
3	Old French	gaiole	prison; gaol; jail
4	Medieval Latin	gabiola	—
5	Late Latin	caveola	—
6	Latin	cavea	hollow, cavity; cage, den, enclosure, stall,...
7	Latin	cavus	hollow, concave; excavated, channeled;...
8	Proto-Italic	kawos	—
9	Proto-Indo-European	ḱowh₁ós	hollow
10	Proto-Indo-European	ḱewh₁-	to swell; to be strong

jailer — Etymology, Origin & Word History | Etymology Explorer