Green’s Dictionary of Slang

tediously moralizing; also as n.

1826		in C.R. Williams A Tour Through the Island of Jamaica 19: Since there was so much preachy preachy, the lazy fellows did nothing but tief.
1862		C. Crosland Mrs. Blake: A Story of Twenty Years 160: I, for one, should never have read anything that looked preachy-preachy.
1887		‘Ouida’ A House Party (1902) 371: You will think me very preachy-preachy, and perhaps you will throw me in the fire unread.
1891		‘’Arry on Wheels’ in Punch 7 May 217/1: Preachy-preachy on ’ealth and fresh air may be nuts to a sanit’ry pot.
1894		G. Moore Esther Waters 124: Sinfulnesss be blowed! I don’t ’old with all them preachy-preachy brethren says about the theatre.
1957		F.G. Cassidy ‘Iteration as a Word-forming Device in Jam. Folk Speech’ in AS XXXII:1 51: preachy-preachy, preaching too much.
2001		L. Burana Strip City 94: A sweaty, warbly-voiced, preachy-preachy God.