1coloquial, marginal, historical A close friend, a partner, an accomplice.
The jack of trumps, the highest-ranking (or second highest-ranking) card in euchre.
In some versions of the game the Joker (known as the best bower) is the highest-ranking card. Compare also left bower.
Early 19th century; earliest use found in Scioto (Ohio) Gazette. From right + bower.