Etymology: plague

From Old French plage, via Latin plaga meaning “wound,” and plangere, meaning, “to strike, or lament.”  Or from the Greek, plaga, meaning, “blow,” as in a hit or strike.  All of these words come from the PIE root plak- (2), meaning “to strike.”  You’ll find this root in words like plankton, complain, and apoplexy.  The word plague came into use in English in the 1540s as a term for a pestilence with many casualties after the bubonic plague began to scourge Europe.