Know how to use "fewer" and "less"? Find out.
"mender of kettles, pots, pans, etc.," mid-13c. (as a surname), of uncertain origin. Some connect the word with the sound made by light hammering on metal. The verb meaning "to keep busy in a useless way" is first found 1650s. Tinker's damn "something slight and worthless" is from 1824, probably simply preserving tinkers' reputation for free and casual use of profanity; more elaborate derivations exist, but seem to be just-so stories without evidence.