Green’s Dictionary of Slang

1. an onion; also in pl., spring onions or sage and onion stuffing.

1890–1904		Farmer & Henley Sl. and Its Analogues VII 277/1: Violet (or Garden-violet) [...] 1. an onion: spec. in pl. = spring onions.
1905		A. Binstead Mop Fair 135: The Bill Willis what the doctor [...] told to eat a raw inion at each meal – him as they used to call ‘Ev’ry-Morn-I-Bring-Thee-Vi’lets.’.
[1915		R. Lardner ‘Alibi Ike’ in Coll. Short Stories (1941) 36: He’d say: ‘Nothin’ like onions for a cold,’ and then he’d dip into the perfumery].
1921		N&Q 12 Ser. IX 425: Violets. Onions.
1931		Pensacola News Jrnl (FL) 27 Aug. 4/4: [cartoon caption] C’mon, Lefty, shake a stump — we gotta gets these violets to the ol’ man.
1939		J. Archibald ‘Dumb is the Word for Willie’ in Popular Detective Aug. 🌐 ‘Six hamburgers, buddy, wit’ plenty of onion, to go out.’ ‘Right. Mike! Stuff the cow-w-w inta six buns with violets! Ship ’em!’.

2. cabbage.

1935

A.J. Pollock Und. Speaks n.p.: Red Mike and violets, corned beef and cabbage.