oportet

Etymology
For, from , causative stem (2nd conjugation) of the root of (3rd conjugation). Some refer the op- to, some to , with which compare the similar expressions  and.

See also, for other examples of words meaning to bind or turn, having derivatives with the sense of obliging.

Verb

 * 1)  to be necessary, proper, becoming; to behoove
 * 2) * oportet nos patriam amare — it behooves us to love our country.
 * 3) * non te oportebat illi argentum reddere — you ought not to have paid him the money.