noun
hand of 9 and 1 in oicho-kabu
A specific scoring combination in the traditional Japanese card game oicho-kabu, where a 9 and a 1 together form a hand.
See also: おいちょかぶ
おいちょかぶで九一が出たら、それは「くっぴん」と呼ばれる役だ。
In oicho-kabu, when a 9 and a 1 come up, that hand is called 'kuppin'.
Oicho-kabu is the card game itself; 九一 is a specific hand within that game.
From the numbers 九 (9) and 一 (1), with the reading くっぴん likely derived from a contraction or sound shift of く (9) and いち (1) to くい → くっ, plus ぴん possibly from 一 (いち) influenced by card-game jargon.