early 15c., "a knocking, colliding; production of sound by a rap," verbal noun from rap (v.1). Meaning "talking, chatting, conversation" is from 1969; meaning "rap music performance" is from 1979, both from rap (v.2).
mid-14c., rappen, "to strike, smite, knock," from rap (n.). Related: Rapped; rapping. To rap (someone's) knuckles "give sharp punishment" is from 1749 (to rap (someone's) fingers in the same sense is by 1670s.). Related: Rapped; rapping.
intransitive, "talk informally, chat in an easy way," 1929, according to OED, popularized c. 1965 in African-American vernacular, possibly first in Caribbean English and from British slang rap (v.) "to say, utter" (by 1879), originally "to utter sharply, speak out" (1540s), ultimately a sense-branch of rap (v.1).
As a noun in this sense from 1898. Meaning "to perform rap music" is recorded by 1979. Related: Rapped; rapping.
<a href="https://www.etymonline.com/word/rapping">Etymology of rapping by etymonline</a>
Harper, D. (n.d.). Etymology of rapping. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/rapping