Douglas Harper's Etymology Dictionary
post restante
direction on mail that it be held at that post office until called for, French, literally "remaining post."
Usage examples of "post restante".
I only discovered at this stage that the Post Office would not redirect mail to a post restante address and required evidence of my address.
Even something of a medium size would have tempted him to take it into a village post office and address it post restante in the U.
Maybe I'll post the damned thing to post restante, Akureyri, and telegraph Slade telling him where to pick it up.