Green’s Dictionary of Slang

romantic, sentimental; also adv.

1896		Ade Artie (1963) 81: Nothin’ mushy, eh? None o’ this soft work?
1906		S. Ford Shorty McCabe 277: Worst of it was, I could feel myself grinnin’ back at her just as mushy.
1909		John Guilpin & Bob Adams ‘Oh You Candy Kid’ 🎵 I know I’m soft and mushy as can be.
1916		‘A-No. 1’ Snare of the Road 19: When you feel as mushy as all that, it’s high time for you to sneak back where you belong, sonny.
1922		Joyce Ulysses 354: First kiss does the trick. The propitious moment. Something inside them goes pop. Mushy like, tell by their eye, on the sly.
1922		B. Hecht A Thousand and One Afternoons [ebook] ‘[T]hey're a pack of selfish, mushy-headed tin horns with fishhook pockets, the kind you can't pull anything out of’.
1927		W. Edge Main Stem 167: That street of forgotten men, as I believe some mushy novelist calls it.
1932		(con. 1910s) J.T. Farrell Young Lonigan in Studs Lonigan (1936) 5: He was Studs Lonigan, a guy that didn’t have mushy feelings.
1941		‘Digg Mee’ ‘Observation Post’ in N.Y. Age 24 May 9/7: Mushy jive ain’t for me.
1949		Wodehouse Mating Season 37: She is the sloppiest, mushiest, sentimentalist young Gawd-help-us.
1957		R. Prather Always Leave ’Em Dying 30: The mushy way they act, they must like each other.
1966		P. Boyle At Night All Cats Are Grey 162: I never in my life heard such mushy talk.
1975		L. Rosten Dear ‘Herm’ 149: The Old Man and ‘Eppie’ are casting mushy goo-goo looks at each other.
1983		J. Byrell (con. 1959) Up the Cross 14: Now, no one had ever sprung Heavy Harold as any sort of [...] romantic. Heavy Harold was just about the least mushy bloke around.
1988		R. Doyle Commitments 7: All tha’ mushy shite abou’ love an’ fields an’ meetin’ mots in supermarkets.
1990		J. Wambaugh Golden Orange (1991) 361: I know what a mushy bastard you are.
2005		J. Stahl I, Fatty 238: Stop me if I’m getting mushy.
2012		(con. 1943) G.S. Manson Irish Fandango [ebook] ‘You haven’t gone mushy on me, have ya?’.