institution (n.) Look up institution at
c. 1400, "action of establishing or founding (a system of government, a religious order, etc.)," from Old French institucion "foundation; thing established" (12c.), from Latin institutionem (nominative institutio) "a disposition, arrangement; instruction, education," noun of state from institutus (see institute (v.)).

Meaning "established law or practice" is from 1550s. Meaning "establishment or organization for the promotion of some charity" is from 1707. Jocular or colloquial use for "anything that's been around a long time" is from 1837.