Green’s Dictionary of Slang

1. (US) the essence, the basics, the ‘brass tacks’; thus meat-and-potato adj., basic, essential.

1960		J. Havoc Early Havoc 56: The place teemed with excitement. This was meat and potatoes. A nice lively cockfight.
1967		Maclean’s (Toronto) July 65: Textbooks remain the meat and potatoes of publishing in Canada.
1975		L. Rosten Dear ‘Herm’ 17: I mean real meat-and-potatoe stuff.
1990		(con. early 1950s) J. Ellroy L.A. Confidential 122: Tryone said lots of things, but let’s get to meat and potatoes.

2. (US) the male genitals, the penis and testicles.

1981		Meat 90: We flopped our meat and potatoes out at the side of the prick-pocket and put ball stretchers on our nuts.
1999		Sydney Morn. Herald 11 Jan. 3/8: Last year they went for the budget $35 suits, but found the cut rather restrictive. ‘We’re willing to pay an extra $35 to have out meat and potatoes comfrotable’ [Simes:DLSS].