early 13c., probably from Old Norse skrapa "to scrape, erase," from Proto-Germanic *skrapojan (cf. Old English scrapian "to scrape," Dutch schrapen, German schrappen), from PIE *skerb-, extension of root *(s)ker- "to cut" (see shear (v.)).
Meaning "gather by great effort, collect with difficulty" is from 1540s. Related: Scraped; scraping. To scrape the bottom of the barrel in figurative sense is from 1942, in reference to U.S. employers facing worker shortages during the war.