Learn English – How and when did the phrasal verb “hit on (someone)” come about

Clarence Major, Dictionary of African American Slang (1970) has this entry for hit on:

Hit on: (1940's–1950's) to make a request, especially for love-making.

Major's subsequent (and much larger) reference work, Juba to Jive: A Dictionary of African-American Slang (1994) provides a more detailed definition:

Hit on v. (1940s–1950s) propose; flirt; make a pass; to make a request, especially for lovemaking; aggressive flirting; sexual harassment. (E[dith] F[olb], R[unnin'] D[own] S[ome] L[ines] [1980], p. 24; P[amela] M[unro], UCLA S[lang: A Dictionary of Slang Words and Expressions Used at UCLA] [1989], p. 49.) S[outhern and] N[orthern] U[se]

J.E. Lighter, The Random House Historical Dictionary of American Slang, volume 2 (1997) has this entry:

hit on, 1.a. to make a sexual proposition to; (broadly) to make any sort of of romantic advance to {The 1931 quot[ation] prob[ably] illus[trates] the colloq[uia;] sense 'to find by chance'. The present sense became widely current in the late 1960's.} [First occurrences:] {1931 L. Zukofsky, in Ahearn Pound/Zukofsky 90: And like one well-fed stud bustin' his harness runs like mad thru Central Park wanting to get drunk, hits on a couple of swell truck horses, sure he's got "it."} 1954 in Wepman, Newman & Binderman The Life 38: Go hit on one of them Indian bitches. 1959 A. Anderson Lover Man 118: She looked so good I felt like hitting on her right then. ...

b. to approach in an attempt to swindle or victimize. [Citations from 1967 and 1970 omitted.]

2. Esp. Black E[nglish] to ask (someone); HIT, 2, above [namely, "to ask (someone) (for something, esp. money or the like); beg from; make a request of; ask; accost"]. [Multiple citations from 1957 forward omitted.]

I don't know what to make of the 1931 quotation from Louis Zukofsky, other than to suspect that it uses "hit on" in a sense much closer to "hit on an idea" than in the sense of "hit on a person." The 1954 and 1959 citations, however, seem entirely on point. The 1954 quotation is evidently drawn from an African American folk poetry/comedy routine that recounts the adventures of two friends who dream of being smooth talkers and big-time operators. The subtitle of The Life is The Lore and Folk Poetry of the Black Hustler; and the same lines appear in Mel Watkins, African American Humor: The Best Black Comedy from Slavery to Today (2002). Here is the relevant portion of the verse routine:

"I want to own New York, and you're not that slick."

"Here, take my money," cried Smitty, "and let me be your trick."

"Be my trick? Why you insult my pride.

Go hit on one of them Indian bitches selling blankets outside."

Robert Chapman & Barbara Kipfer, Dictionary of American Slang, third edition (1995) has this entry:

hit on someone 1 v phr by 1970s To ask for a favor; solicit; pester; =HIT someone: [example omitted] 2 v phr 1980s students To make advances to; =PROPOSITION: [examples omitted]

I first encountered the expression "hit on [her]" in the song "I'm a Roadrunner" as sung by Bill Cosby on his 1968 album Hooray for the Salvation Army Band. You can hear that instance (with a bit of context before and after) in this YouTube video, at approximately 1:22–1:39.

Whether Major is correct that the "lovemaking" sense of "hit on" goes all the way back to the 1940s, it was certainly in place in some varieties of U.S. Black English by 1954—long before Chapman & Kipfer's attribution of it to U.S. students in the 1980s.