beau / bō/ • n. (pl. beaux / bōz/ or beaus) dated 1. a boyfriend or male admirer.2. a rich, fashionable young man; a dandy.

beau a rich, fashionable young man, a dandy; sometimes used in a personal appellation, as in Beau Brummell, Beau Nash. Recorded from the late 17th century, the word comes from French, literally ‘handsome’, from Latin bellus.
Beau Geste the nickname of Michael Geste (punning on beau geste a noble and generous act) who in P. G. Wren's romantic adventure novel (1924) of this title runs away to enlist in the French Foreign Legion to spare his family the distress of a wrongful accusation against him.

beau dandy XVII; lady's suitor XVIII. — F. :- L. bellus pretty, fine. Cf. BELLE.