Terrapin is a family of Decktet betting games based in which you try to avoid getting every suit. It has been described by some players as Blackjack meets Texas Hold 'em - you want to get a better hand, but every card you add increases the chance you'll get Turtle Butt.
An earlier version of Terrapin was known simply as Turtle Butt. That's still the name for a hand which has one of every suit, a hand which has gone bust.
There are several Terrapin games that use the same rules for ranking hands but different rules for betting.