Bad Etymology

Plan, n. a formalised bureaucratic aspiration, from Latin planus, a plane; hence something expected to fly which will eventually fall flat.

Trust, n. a necessary attitude in the striking of bargains; related to tryst, derived from Old French triste, unhappy, thus an assignation at which sex is negotiated, bought and sold. Cf. trust fund, n., a down payment by the resentful rich on the misery of future paupers.