Green’s Dictionary of Slang

bossy n.

[Lat. bos, ox]

(US tramp) beef; thus bossy in a bowl, beef stew.

[US]Day Book (Chicago) 8 Sept. 17/1: ‘Beef stew and a cup of tea for me’ [...] ‘Bossy in a bowl —boiled leaves on the side’.
[as cite 1916].
[US]Irwin Amer. Tramp and Und. Sl. 35: Bossy. – Beef, as a food. From Latin, bos, an ox, whence ‘Bovril,’ ‘bovex.’ [...] Bossy in a Bowl. – Beef stew.