mid-15c., "confined condition," from close (adj.) + -ness. Meaning "stuffiness" (of air) is from 1590s; meaning "nearness" is from 1716.[closeness etymology, closeness origin, 英语词源]
1550s, "full of stuff, full of substance" (obsolete); 1831 as "poorly ventilated;" from stuff (n.) + -y (2). Sense of "pompous, smug" is from 1895. Related: Stuffily; stuffiness.