mid-14c., "living together, having dealings with others," also "manner of conducting oneself in the world;" from O.Fr. conversation, from L. conversationem (nom. conversatio) "act of living with," from conversat-, pp. stem of conversari "to live with, keep company with," lit. "turn about with," from L. com- "with" (see com-) + vertare, frequentative of vertere (see versus). Specific sense of "talk" is 1570s. Used as a synonym for "sexual intercourse" from at least 1511, hence criminal conversation, legal term for adultery from late 18c. Related: Conversationalist; conversationist.
My question is "how did it come to mean 'talk' in the 1570s?"