faculty (n.) Look up faculty at Dictionary.com
late 14c., "ability, means, resources," from Old French faculté (14c.) "skill, accomplishment, learning," and directly from Latin facultatem (nominative facultas) "power, ability, wealth," from *facli-tat-s, from facilis (see facile).

Academic sense "branch of knowledge" probably was the earliest in English (attested in Anglo-Latin from late 12c.), on notion of "ability in knowledge." Originally each department was a faculty; the use in reference to the whole teaching staff of a college dates from 1767.