bona-roba n.

"money or other benefit given as a premium or extra pay to reward or encourage work," 1773, a phrase in "Stock Exchange Latin" [Weekley], taken as "a good thing," from Latin bonus "good" (adj.), perhaps originally "useful, efficient, working," from Proto-Italic *dw-eno- "good," probably a suffixed form of PIE root *deu- (2) "to do, perform; show favor."

The correct noun form would be bonum. Specifically as "extra dividend paid to shareholders from surplus profits" from 1808. In U.S. history the bonus army was the name given to the tens of thousands of World War I veterans and followers who marched on Washington, D.C., in 1932 demanding early redemption of their service bonus certificates (which carried a maximum value of $625).

"long, loose outer garment reaching almost to the floor, worn by men or women over other dress," late 13c., from Old French robe "long, loose outer garment" (12c.), from a Germanic source (compare Old High German rouba "vestments"), from West Germanic *raubo "booty" (cognate with Old High German roub "robbery, breakage"), which also yielded rob (v.).

Presumably the notion is of fine garments taken from an enemy as spoil, and the Old French word had a secondary sense of "plunder, booty," while Germanic cognates had both senses; as in Old English reaf "plunder, booty, spoil; garment, armor, vestment."

The meaning "dressing gown" is from 1854; such extended senses often appear first in French, e.g. robe de chambre "dressing gown," robe de nuit "nightgown." From c. 1300 in reference to official vestments and thus indicative of position or membership in a religious order, guild, etc.; metonymic sense of The Robe for "the legal profession" is attested from 1640s.