Is it farther or further?
c.1400, "causing pain," from Old French doloros (12c., Modern French douloureux) "painful, sorrowful, wretched," from Late Latin dolorosus "painful, sorrowful," from Latin dolor "pain, grief." Sense of "causing grief" is from mid-15c.; that of "full of sorrow" is from 1510s. Related: Dolorously; dolorousness.