Meaning

noun any undertaking that is easy to do

noun stable gear consisting of a band around a horse's belly that holds the saddle in place

noun a form of all fours in which the players bid for the privilege of naming trumps

originCompare senses at etymology 1 (a girth, a tight grip), perhaps suggesting the tactics used in the game; or perhaps from Spanish cinco (“five”), the five spots of the colour of the trump being important cards.

Etymology from Wiktionary, CC BY-SA 3.0