man up

Meanings

1. To be brave or tough enough to deal with something in a manner that is considered strong or manly. (Compare man (“brace oneself, steel oneself”))
2. (Of personnel) to assemble, each person manning (attending to) his station, prepared for the departure of an aircraft, ship, etc. (Compare man (“supply with staff; take up position to operate”).)
3. To staff adequately; to staff up; to successfully fill all needed labor positions. (Compare man (“supply with staff”).)
4. To vigorously guard the opponent to whom one is assigned.

Etymology

From man + up, with influence from own up, buck up.