Green’s Dictionary of Slang

1. a temper, a tantrum.

1882		‘F. Anstey’ Vice Versa (1931) 78: I went on calmly smoking my cigar as if nothing was the matter. That put the Proctor in a bait, I can tell you!
1899		Kipling ‘The Moral Reformers’ Complete Stalky & Co. (1987) 134: ‘What a bait you’re in!’ said Stalky. ‘Keep your hair on, Beetle.’.
1914		‘Ian Hay’ Lighter Side of School Life 184: When he gets in a bait about anything it is always a sound plan to get him to talk about one of these rotten things.
1946		(con. 1912) B. Marshall George Brown’s Schooldays 25: I bet you’re funked to send your plate up in case the Bruiser loses his bate with you.
1950		A. Buckeridge Jennings Goes To School 29: It’s wizard – well, it is if it’s somebody else he’s in a bate with and not you.
1958		Willans & Searle Complete Molesworth (1985) 90: They lose their tempers and get into a terrific bate.
1969		A. Buckeridge Trust Jennings (1989) 94: I bet Old Wilkie’s in a frantic bate.
1978		(con. 1940s) J.G. Farrell Singapore Grip 110: That’s no reason to get in a bate.
1981		W. Boyd Good Man in Africa 230: ‘Arthur wants to see you, Morgan. I think he’s in a bit of a bate’.

2. any form of mood, no anger implied.

1958

Willans & Searle Complete Molesworth (1985) 240: Headmaster is in a good bate.