What have we stopped noticing?
The things we say, do, and accept without thinking twice.
Look closer where it comes from, what it assumes, and the case for keeping it
What you mean by it
A measure of labor time. See also manpower, man-days, manned.
What it's actually picturing
The generic term uses “man” as the standard human unit.
What it takes for granted
That the standard unit of a human being is a man, so everyone else is counted in units named after someone else.
Worth knowing
The technical meaning is clear, and “person-hours” is already established.
The case for keeping it
Old English “man” meant “person” of any sex, and that sense survives in words like “mankind”. But “manpower” dates only to 1855, when “man” already mostly meant a male.
Say it plainly
Person-hoursWork hoursStaffing