mid-14c., "to move about, live, dwell; live or behave in a certain way" (senses now obsolete), from Old French and French converser "to talk, open communication between," also "to live, dwell, inhabit, reside" (12c.), and directly from Latin conversari "to live, dwell, live with, keep company with," passive voice of conversare, literally "to turn round with," from assimilated form of com "with, together" (see con-) + versare, frequentative of vertere "to turn" (from PIE root *wer- (2) "to turn, bend").
Sense of "to communicate (with)" in English is from 1590s; that of "talk informally with another" is from 1610s. Related: Conversed; conversing.
"turned about, transposed, reciprocal," 1560s, originally mathematical, from Latin conversus "turned around," past participle of convertere "to turn about, turn around, transform," from assimilated form of com "with, together" (see con-) + vertere "to turn" (from PIE root *wer- (2) "to turn, bend"). From 1794 as "opposite or contrary in direction." Related: Conversely.
c. 1500, "acquaintance by frequent or customary intercourse," from converse (v.). From 1610s as "conversation, familiar discourse."
1550s, originally in mathematics, from converse (adj.). From 1786 as "thing or action that is the exact opposite of another." As an example, Century Dictionary gives "the hollows in a mold in which a medal has been cast are the converse of the parts of the medal in relief." Chaucer has in convers, apparently meaning "on the other side."