Green’s Dictionary of Slang

1. to lay money down; the inference is of doing so with force or energy.

1855		F.C. Adams Our World 225: Every man purchasing is expected to have his shiners ready, so that he can plunk down cash in ten days.
1882		Chronicle XIII 127/2: He will imbibe the rock and the rye, but he will make a wry face when he has to ‘plunk down the rocks’ to pay for the rock and rye.
1891		S.B. Elliott Jerry 162: We never had no money to plunk down all at onest fur the lan’.
1900		E.H. Babbitt ‘College Words and Phrases’ in DN II:i 50: plunk, v. To pay; in phrase to plunk down.
1911		Bisbee Dly Rev. (AZ) 26 Nov. 15/5: Ef there’s any more of you [...] wants to pay me what you owe me [...] just walk up here an’ plunk down.
1912		R.W. Brown ‘Word-List From Western Indiana’ in DN III:viii 585: plunk, v. To throw or ‘plank’ down. ‘He plunked down the cash for it.’.
1934		R. Sale ‘A Nose for News’ in Goulart (1967) 202: Suckers were plunking down the coppers and having them swept away without a bit of return.
1946		(con. 1910s) J. Thompson Heed the Thunder (1994) 111: He don’t step over to the hotel and plunk down maybe a nickel a meal in hard cash.
1958		E. Dundy Dud Avocado (1960) 239: I plunked down the 3,000 francs for it and picked it up.
1989		Kirk & Madsen After The Ball 302: Most of us think nothing of plunking down ten dollars for a cover charge and two drinks.

2. (also plunk) to wager.

1899–1900		C.L. Cullen Tales of the Ex-Tanks 180: He plunked his first hunk of gilt, twenty dollars, on a queen.
1931		B. Lubbock Bully Hayes 12: John Anderson [...] plunked down his whole wad in one bet.
1956		‘Toney Betts’ Across the Board 99: He plunked the whole bankroll on a 2 to 1 shot in the last race. [Ibid.] 241: An iceman entered the office and plunked down twenty-five dollars for a horse.

3. (also plunk) to sit down, to put down.

1907		Peterhead Sentinel 30 Nov. 7/1: I found my self [...] tumbling and stotting [...] and anon slipping and plunkin’ doon on my hurdies.
1929		M. Levin Reporter 18: The woman was plunked across the hallway.
1936		(con. 1830s–60s) ‘Miles Franklin’ All That Swagger 115: Danny took a position in the big yard, plunking his hat on his head and planting his peg stoutly in the ground.
1941		A. Lomax Mister Jelly Roll (1952) 208: Anytime that a person can get up out of bed in the middle of the night and just plunk his hand on a piano and begin to write something and have a tune, he’s wonderful to me.
1951		M. Spillane One Lonely Night 67: I ambled over and plunked in a seat.
1955		J.P. Donleavy Ginger Man (1958) 163: He walked under the three gold balls and to the counter. Plunked down the two decanters.
1960		Kerouac letter 13 Sept. in Charters II (1999) 277: Some crazy artist plunk a hat on his hand and made him look like ‘Jessie James’.
1979		B. Gutcheon New Girls (1982) 22: ‘Now, Muffin,’ said Lisa, plunking down on the bed beside her.
1991		B. Hamper Rivethead (1992) 83: Each afternoon I’d plunk myself down in front of my mom’s old Underwood typewriter.
1998		L. Stringer Grand Central Winter (1999) 156: She plunks the receiver down. [Ibid.] 161: Emerald plunks back down in her chair.
2000		F. Kellerman Stalker (2001) 53: She plunked a beer in front of Oliver.

4. to sit someone down.

2005

J. Stahl I, Fatty 189: I’m plunked down behind a battered desk, 100 watts in my face.

(US) to opt for, to give one’s support to.

1941

B. Schulberg What Makes Sammy Run? (1992) 98: All I know is either you plunk for Merriam around here or you’re a dead pigeon.