Green’s Dictionary of Slang

1. (orig. US) to flatter, to charm, thus soft-soaping, flattery.

1842		Whip & Satirist of NY & Brooklyn (NY) 14 May n.p.: This fellow [...] is easily duped, or what the gals here call ‘soft-soaped’.
1847		Bell’s Life in Sydney 4 Dec. 2/6: Patrick Mccarthy, apprenticed to the ‘soft-soaping’ and ‘cutting it fat’ profession.
1848		W.E. Burton Waggeries and Vagaries 14: Jest to see if he couldn’t soft soap the young critter out of a leetle rhino.
1858		G.W. Harris ‘Letter from S---L, of Tennessee’ Nashville Union and American XXIX July in Inge (1967) 90: After softsoaping the two old spectacled gourd heads about their intelligence [...] he drew from his saddle bags a greasy copy of ‘Cobb’.
1868		‘It’s Astonishing How It Is Done’ in My Young Wife and I Songster 14: I soft-soaped her over, and very soon could see, / My gammon caused her soft heart to relent.
1878–9		A. Garcia Tough Trip Through Paradise (1977) 101: He tried to soft-soap me.
1880		Bulletin (Sydney) 13 Mar. 4/1: By soft-soaping Sir Henry a little bit, he has managed to get on the blind side of the Premier, who has promised to make it all right with the worthy ciphers, his colleagues.
1882		Taunton Courier 1 Mar. 13/1: [W]hether a trifle more variety in the dramatic criticisms of our own daily papers wouldn’t be an improvement. Their uniform ‘soft soaping’ is just a bit too monotonous [...] couldn't they do a ‘blow up’ say, once in a decade or so?
1890		Music Hall & Theatre Rev. 1 Mar. 9/1: ‘Let us take one at a time—soft-soap the theatrical managers, and then we can beat the music-hall fraternity’.
1894		Truth (Sydney) 23 Dec. 3/1: Mr Darling soft-soaps him with plenty of promises, but fails to carry any of them out.
1897		Ranche & Range (N. Yakima, WA) 15 Apr. 8/2: Let them know we are not to be soft-soaped [...] Americans like fair play.
1905		‘Central Connecticut Word-List’ in DN III:i 20: soft-soap, v. To flatter.
1911		G. Bronson-Howard Enemy to Society 326: Meanwhile, I’ll leave you all to soft-soap the heir.
1922		Joyce Ulysses 73: You and me, don’t you know? In the same boat. Soft soaping.
1927		R. Lardner ‘Hurry Kane’ in Coll. Short Stories (1941) 94: Then Dave soft-soaped him, told him how he’d burn up the league.
1939		V. Davis Gentlemen of the Broad Arrows 79: Ignoring the Principal’s attempt at ‘soft-soaping’ him.
1949		W.R. Burnett Asphalt Jungle in Four Novels (1984) 124: I’ve called you here not to soft-soap you and tell you what smart [...] guys you are.
1957		J. Braine Room at the Top (1959) 113: In business, I ruminated, I’d have to soft-soap people whom I despised.
1969		B. Mason Awatea (1978) 75: See? Patronage. Soft-soap them.
1979		F. Norman Too Many Crooks Spoil the Caper 12: Bullying people and soft-soaping them by turns is standard procedure at Scotland Yard.
1981		A. Payne ‘You Need Hands’ in Minder [TV script] 16: Arthur soft-soaping Matthews.
1991		B. Quinn Smokey Hollow 129: He refused to softsoap anybody.
2001		(con. 1964–8) J. Ellroy Cold Six Thousand 528: I figured you’d try to softsoap me about Lyle. The ‘you lost a brother, I lost a friend’ routine.

2. (US) to play down, to minimize.

2012

T. Piccirilli Last Kind Words 144: Should I soft-soap my worries over Butch or ask her flat out if she knew he was a punk working for Danny Thompson.