E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Scrape an Acquaintance (To).
The Gentlemans Magazine says that Hadrian went one day to the public baths, and saw an old soldier, well known to him, scraping himself with a potsherd for want of a flesh-brush. The emperor sent him a sum of money. Next day Hadrian found the bath crowded with soldiers scraping themselves with potsherds, and said, Scrape on, gentlemen, but youll not scrape acquaintance with me. (N. S., xxxix. 230.)