coincidence (n.)

c. 1600, "exact correspondence in substance or nature," from French coincidence, from coincider, from Medieval Latin coincidere, literally "to fall upon together," from assimilated form of  Latin com "with, together" (see com-) + incidere "to fall upon" (from in- "upon" + combining form of cadere "to fall," from PIE root *kad- "to fall").

From 1640s as "occurrence or existence during the same time." Meaning "a concurrence of events with no apparent connection, accidental or incidental agreement" is from 1680s, perhaps first in writings of Sir Thomas Browne.