c.1225, "vows taken upon entering a religious order," from O.Fr.
profession, from L.
professionem (nom.
professio) "public declaration," from
professus (see
profess). Meaning "occupation one professes to be skilled in" is from 1541; meaning "body of persons engaged in some occupation" is from 1610; as a euphemism for "prostitution" (e.g.
oldest profession) it is recorded from 1888.
Professional (adj.) is first recorded 1747 with sense of "pertaining to a profession;" 1884 as opposite of
amateur. As a noun, it is attested from 1811.
Professionalism is from 1856.