means To successfully defeat, master, or get past an obstacle, opponent, or overwhelming feeling.

from A straightforward Old English compound: 'ofer' (over) plus 'cuman' (to come) — literally to 'come over' something, the way a victor comes over a fallen foe or a wave comes over a wall. 'Cuman' is the same ancient root that gives us 'come,' so the image is bodily and old: you arrive on top of the thing that opposed you. The figurative sense of being overwhelmed by emotion ('overcome with grief') is a later softening of that same conquering motion.