singleton

singleton
https://eow.alc.co.jp/search?q=singleton

singleton
https://en.wiktionary.org/wiki/singleton

(playing cards) A playing card that is the only one of its suit in a hand, especially at bridge.

From single + -ton, probably following the model of simpleton.

suit
wikipedia:スート

simpleton
https://en.wikipedia.org/wiki/Simpleton

THE SINGLETON
https://www.kirin.co.jp/products/whisky_brandy/singleton/

非常になめらかで親しみやすいシングルモルトに仕上がっています。