1590s, "affecting the emotions or affections, moving, stirring" (now obsolete in this broad sense), from French pathétique "moving, stirring, affecting" (16c.), from Late Latin patheticus, from Greek pathetikos "subject to feeling, sensitive, capable of emotion," from pathetos "liable to suffer," verbal adjective of pathein "to suffer" (from PIE root *kwent(h)- "to suffer").
The specific meaning "arousing pity, sorrow, or grief" or other tender feelings is from 1737. The colloquial sense of "so miserable as to be ridiculous" is attested by 1937. Related: Pathetical (1570s); pathetically. The pathetic fallacy (1856, first used by Ruskin) is the attribution of human qualities to inanimate objects.