Old English furthor (adverb), furthra (adjective), fyrthrian (verb), of Germanic origin; related to forth
Is there any difference between further and farther in she moved further down the train and she moved farther down the train? Both words share the same roots: in the sentences given above, where the sense is ‘at, to, or by a greater distance’, there is no difference in meaning, and both are equally correct. Further is a much commoner word, though, and is in addition used in various abstract and metaphorical contexts, for example referring to time, in which farther is unusual, e.g. without further delay; have you anything further to say?; we intend to stay a further two weeks. The same distinction is made between farthest and furthest: the farthest point from the sun versus this first team has gone furthest in its analysis.