The story
From Forstner (proper noun) + bit (noun). Named after American inventor, gunsmith and merchant Benjamin Forstner (1834–1897). First attested after 1886.
Etymology from Wiktionary, CC BY-SA 4.0.
Forstner bit
Today it means: A kind of drill bit that bores precise flat-bottomed holes in wood, in any orientation with respect to the grain. Full definition →