scrape off
刮 centers on removing a surface layer by scraping: to scrape off, shave, or plane away material.
刮 combines 舌 (tongue) and 刂 (knife), suggesting scraping with a blade. The exact historical development is uncertain, but the component combination likely expresses the action of scraping or shaving.
A tongue 舌 and a knife 刂 together: imagine scraping your tongue with a knife to clean it off. That's scraping off.
For カツ, imagine scraping off a stubborn sticker with a sharp cut: cut -> カツ, and the knife scrapes it clean.