Green’s Dictionary of Slang

1. (orig. boxing jargon) a solid, hard blow [? it sends the victim to the floor].

1849		Paul Pry 12 Feb. n.p.: Paul Advises [...] Two young milliners [...] when taking their nocturnal perambulations, to study a little more decorum, and not make such frequent use of ‘I gave him sich a sender’ [or] ‘Oh, that's stunning!’.
1865		Leaves from Diary of Celebrated Burglar 115/2: At this moment, Artful, who had recovered from the ‘sender’ Joe had dealt him, was in the act of dealing my ‘pal’ a ‘stunner’ with an empty wine bottle.
c.1880		New Song and Dialogue on Bloomerism 1: Take that, said she, and she gave me such a sender under the mug, which sent me sprawling.

2. (US black) a person (usu. a musician) or thing (usu. a record) who or which is emotionally arousing [send v.].

1935		Vanity Fair (N.Y.) Nov. 71: Hot artists that can put across their licks successfully are ‘senders’.
1935		Ted Yates This Is New York 3 May [synd. col.] That cocktail soiree at the Danceland [...] was a ‘sender’.
1936		A.E. Duckett ‘Truckin ’round Brooklyn’ in N.Y. Age 18 Jan. 7/1: Mac Jones is another sender at the spot...His comedy skits are mellow.
1938		N.E. Eliason ‘Some Negro Terms’ AS XIII:2 152/1: Sender: anything that gives an emotional thrill.
1941		Cab Calloway ‘Hep Cat’s Love Song’ 🎵 You’re a sender, honey! / Everybody knows that I’m wild about you!
1942		Z.N. Hurston ‘Story in Harlem Sl.’ Novels and Stories (1995) 1010: Sender: he or she who can get you to go, i.e., has what it takes Used often as a compliment: ‘He’s a solid sender’.
1953		W. Fisher Waiters 76: He looked at her dress [...] ‘It’s a sender,’ Asher said admiringly.