early 15c., vesten (implied in vested), "to put in possession of a person," from Anglo-French vester, Old French vestir "to clothe; get dressed," Medieval Latin vestire "to put into possession, to invest," all from Latin vestire "to clothe, dress, adorn."

This is related to vestis "garment, clothing" (according to Watkins from suffixed form of PIE *wes- (2) "to clothe," extended form of root *eu- "to dress"). Related: Vesting.

The meaning "clothe with or as with a garment" is by 1640s (implied in vested); that of "invest or clothe as with authority" by 1670s.

1610s, "loose outer garment" (originally in reference to ones worn by men in Eastern countries or in ancient times), from French veste "a vest, jacket" (17c.), from Italian vesta, veste "robe, gown," from Latin vestis "clothing," from vestire "to clothe" (from PIE *wes- (2) "to clothe," extended form of root *eu- "to dress").

The modern sleeveless garment worn by men beneath the coat was introduced in England by Charles II in a bid to rein in men's attire at court, which had grown extravagant and decadent in the French mode.

The King hath yesterday, in Council, declared his resolution of setting a fashion for clothes .... It will be a vest, I know not well how; but it is to teach the nobility thrift. [Pepys, diary, Oct. 8, 1666]

(Louis XIV of France is said to have mocked the effort by putting his footmen in such vests.) As an outer garment for women, by 1706. Vest-pocket (adj.), figurative of something small of its sort, is by 1823.