complain (v.)
late 14c., "find fault, lament," from stem of Old French complaindre "to lament" (12c.), from Vulgar Latin *complangere, originally "to beat the breast," from Latin com-, intensive prefix (see com-), + plangere "to strike, beat the breast" (from PIE root *plak- (2) "to strike"). Older sense of "lament" died out 17c. Related: Complained; complaining.