right hand (n.)
the hand opposed to the left hand, late Old English rihthand; see right (adj.2) + hand (n.). So called as the one normally the stronger of the two. Applied to the right side generally by c. 1200. As a symbol of friendship or alliance, by 1590s. Figurative for "indispensable helper, person of use or importance," 1520s (right-hand man is attested by 1660s). Right-handed "having the right hand more useful than the left" is attested from late 14c.; as an adjective from c. 1700. Right-hander, of persons, "one who uses the right hand more skillfully than the left" is by 1885.