Green’s Dictionary of Slang

to talk wildly, noisily.

1838		Knickerbocker Mag. Sept. 282: I’ll keep dark about it, you may depend, says I. I’m not a man that can’t keep nothin’ in my gizzard, but go right off and blart out all I hear.
1843		Gleaner (Manchester, NH) 13 May n.p.: It would be [...] a real kindness to the audience if he would not blart till he got home.
1853		T. Haliburton Sam Slick’s Wise Saws I 160: Blartin’ out a discovery afore you take a patent may help others, but it keeps you poor.
1873		W.H. Thomes Bushrangers 134: You is sure that you isn’t a spy? that you didn’t come here to see what you could see, and then go off and blart like a bloody sheep?
1948		J. O’Connor Come Day – Go Day (1984) 99: Quit your whinging [...] What are you blerting about?
1968		A. Burgess Enderby Outside in Complete Enderby (2002) 302: Your name I know but I won’t blart it.