Green’s Dictionary of Slang

to lose one’s temper (suddenly), to speak forcefully.

1834		York Herald 3 May 4/3: Taylor [...] an old lag on the town, ‘flared up’ at this intelligence.
1835		‘Kate Randy’ in Secret Songster 6: Such a regular good blowen to flare up.
1849		F.S. Mahony Reliques Father Prout I 319: Vert-Vert, the Parrot. Forth like a Congreave rocket burst, And storm’d and swore, flared up, and curs’d [F&H].
1854		Thackeray Newcomes I 124: He was in the Cave of Harmony, he says, that night you flared up about Captain Costigan.
1860		R. Nicholson Rogue’s Progress (1966) 177: Rowley, to use a common phrase, ‘flared up’ and floored the innocent wight.
1861		(con. 1840s–50s) H. Mayhew London Labour and London Poor I 360/2: Ask any on ’em if they know anything about old Tom, the collar-maker, and see if they don’t flare up and respect me.
1870		Sportsman (London) 9 Apr. 4/1: Dr Begg [...] . [...] ‘flares up’ occasionally, and shows very clearly that he has no valid reason for his objection.
1907		J.W. Carr ‘Word-List from Hampstead, NH’ in DN III iii 187: flare up, v. To become angry.
1914		Bulletin (Sydney) 8 Oct. 14/1: Finally preparations were begun to tar his blankets, and then Moore flared up. In three whirlwinds he outed the shed bully, a presser and the slushy, and chased Morgan over the horizon.