O.E. sar "painful, grievous, aching," infl. in meaning by O.N. sarr "sore, wounded," from P.Gmc. *sairaz (cf. O.Fris. sar "painful," M.Du. seer, Du. zeer "sore, ache," O.H.G. ser "painful"), from PIE base *sai- "suffering" (cf. O.Ir. saeth "pain, sickness"). Adv. use (e.g. sore afraid) has mostly died out (except as sorely), but remains the main meaning of Ger. cognate sehr "very." Slang meaning "angry, irritated" is first recorded 1738; sorehead "mean, discontented person" is first recorded 1848, Amer.Eng.
O.E. sar "bodily injury, sickness, disease, pain, suffering," from root of sore (adj.). Now restricted to ulcers, boils, blisters.