sorrel (adj.)

"reddish brown," especially of horses, mid-14c., from Old French sorel, from sor "yellowish-brown," probably from Frankish *saur "dry," or some other Germanic source, from Proto-Germanic *sauza- (source also of Middle Dutch soor "dry," Old High German soren "to become dry," Old English sear "withered, barren;" see sere). Perhaps a diminutive form in French.

small perennial plant, late 14c., from Old French surele (12c., Modern French surelle), from sur "sour," from Frankish *sur or some other Germanic source, from Proto-Germanic *sura- "sour" (source also of Old High German, Old English sur "sour;" see sour (adj.)). So called for the taste of its leaves.