from
The Collaborative International Dictionary of English v.0.48
Cinch \Cinch\, n. [Cf. cinch a girth, a tight grip, as v., to
get a sure hold upon; perh. so named from the tactics used in
the game; also cf. Sp. cinco five (the five spots of the
color of the trump being important cards).]
A variety of auction pitch in which a draw to improve the
hand is added, and the five of trumps (called right pedro)
and the five of the same color (called left pedro, and
ranking between the five and the four of trumps) each count
five on the score. Fifty-one points make a game. Called also
{double pedro} and {high five}.
[Webster 1913 Suppl.]