niacin (n.)
"pellagra-preventing vitamin in enriched bread," 1942, coined from ni(cotinic) ac(id) + -in (2), chemical suffix; suggested by the American Medical Association as a more commercially viable name than nicotinic acid.
The new name was found to be necessary because some anti-tobacco groups warned against enriched bread because it would foster the cigarette habit. ["Cooperative Consumer," Feb. 28, 1942]