1560s, "to move and act unconsciously;" 1580s, "to be listless and apathetic," the sound of the word perhaps somehow suggestive of low feelings (compare mop (v.) "make a wry mouth" (1560s); Low German mopen "to sulk," Dutch moppen "to grumble, to grouse," Danish maabe, dialectal Swedish mopa "to mope"). Related: Moped; moping; mopey; mopish.