Green’s Dictionary of Slang

armstrong heater n.

[a pun on SE strongarm and the brand-name of a stove]

(US) one’s arms, when embracing a loved one.

1932
19401950196019701980
1988
[US]J.L. Kuethe ‘Johns Hopkins Jargon’ in AS VII:5 329: armstrong heaters — arms when used to hold a girl.
J. West Witch Diggers 184: Dandie put both arms around her. ‘I’m her red-hot Armstrong heater,’ he said.
I. Wallem I Have a Place (1992) 46: After the engine stopped and lights were out, Henry would move a few inches closer and say, ‘How about a little Armstrong Heater?’.