(idiomatic,dated)Used in place of a real explanation when excusing oneself for a short period of time, particularly (euphemistic) to use a toilet or (historical) drink alcohol.
I'll be right back. I've just got to go to the ladies' room to see a man.
1867 September 12, Ball Players' Chronicle, p. 3:
Although they were all out, at the bases, and the rest of our nine having gone to see a man there was nobody to take the bat.