side bet

noun

1. a bet made, as with another player, in addition to one's principal bet:

   a side bet as to which of us would draw the highest card.

Word History and Origins

Origin of side bet¹

First recorded in 1890–95

Example Sentences

But the bones dont roll right that the side bet dont go for Johnson instead of Applegoat.

From Project Gutenberg

In all probability they are now agitating for the two shillings' increase to enable them to have a little side bet.

From Project Gutenberg