grati

Grati is transitive and light. You drag something sharp or rough across a surface without cutting into it: a cat at a door, a fingernail at an itch, a prisoner's name into a wall. If you break the surface you have moved on to vundi, to wound, or tranĉi, to cut. The noun grato is both the act and the mark it leaves, so a scratch on a car door is a grato.

The false seam, and it is the dangerous kind. Grati looks like the root inside gratuli, to congratulate, and the two have nothing to do with each other. Gratuli came from Latin gratulari, built on gratus meaning pleasing, the family that also gave English grateful and gratitude. Grati came from Frankish by way of French gratter and is about fingernails. Congratulating somebody and scraping them are not the same gesture, whatever the spelling suggests.

Two more in the same corner worth keeping apart. Skrapi is to scrape properly, with force and usually to remove something; froti is to rub, with no sharp edge involved at all. Grati sits between them, and it is the one that itches.