1870 in the anatomical sense, noun of action from Latin fenestrare, from fenestra "window, opening for light," a word perhaps from Etruscan (see defenestration). Meaning "arrangement of windows" as a design element in architecture is from 1846. Related: Fenestrated.

late 14c., "pertaining to windows," from Old French fenestral, from fenestre "window," from Latin fenestra (see fenestration).