Absent or otherwise unavailable: I'm out of the pocket for a bit, but I'll get back at ya(1974+)
The Dictionary of American Slang, Fourth Edition by Barbara Ann Kipfer, PhD. and Robert L. Chapman, Ph.D. Copyright (C) 2007 by HarperCollins Publishers. Cite This Source
Idioms and Phrases with out of pocket
Lacking money; also, having suffered a financial loss, as in We can't go; I'm out of pocket right now. William Congreve had it in The Old Bachelor (1693): “But egad, I'm a little out of pocket at present.”
[ Late 1600s
Referring to actual money spent, as in I had to pay the hotel bill out of pocket, but I know I'll be reimbursed. This expression sometimes occurs as a hyphenated adjective mainly in the phrase out-of-pocket expenses, as in My out-of-pocket expenses for business travel amounted to more than a thousand dollars.
[ Late 1800s