The English word 'far' traces from Old English 'feorr' (distant, remote) through Proto-Germanic *ferrai to one of the most prolific roots in the Indo-European language family: PIE *per-, meaning 'forward,' 'through,' 'across,' or 'beyond.' This root is the ultimate source of a staggering number of English words — not only 'far' but also 'for,' 'fore,' 'from,' 'forth,' 'first,' 'further,' 'furnish,' 'furniture,' and the prefixes 'per-,' 'pre-,' 'pro-,' 'fore-,' and 'para-.' Few roots have scattered as many descendants through the English vocabulary.
The Old English form 'feorr' shows the typical West Germanic development of PIE *per- with an intensive r-suffix (*per-ro-), giving the sense of 'very much forward' → 'far away.' The word was a common adjective and adverb throughout the Old English period, appearing in Beowulf and other early texts. The Middle English form 'fer' eventually gave way to 'far,' with the vowel change reflecting dialectal variation — the 'a' form, originally northern, became standard.
The Germanic cognates are consistent: German 'fern' (far, distant), Dutch 'ver' (far), Old Norse 'fjarri' (far), and Gothic 'fairra' (far). German preserves the root productively in 'Fernseher' (television — literally 'far-seer'), 'Fernrohr' (telescope — 'far-tube'), and 'Ferngespräch' (long-distance call — 'far-conversation').
Outside Germanic, the PIE root *per- produced an equally vast family. Latin 'per' (through, by means of) gave English 'per-,' 'percent,' 'perfect,' 'perform,' 'permeate,' and scores of others. Latin 'prae' (before, in front of) — from *per- with a different ablaut grade — gave 'pre-,' 'previous,' 'predict,' 'prefer.' Latin 'prō' (for, forward) gave 'pro-,' 'provide,' 'produce,' 'promote.' Greek 'peri' (around, about) gave 'perimeter,' 'periphery,' 'period.' Greek 'para' (beside, beyond) gave 'parallel,' 'paradox,' 'parasite.' Sanskrit 'paras' (farther, beyond) and 'pūrva' (former, first) continue
The comparative and superlative forms of 'far' present one of English's well-known irregularities. The older forms are 'farther/farthest,' but 'further/furthest' (from Old English 'furðra,' with a different vowel grade of the same root) has become interchangeable in most contexts. Style guides sometimes distinguish 'farther' for physical distance and 'further' for figurative extension ('further discussion'), but this distinction is widely ignored in practice and has no strong historical basis — both forms derive from the same PIE root.
The compound 'farewell' is literally 'fare well' — a wish that someone travel (fare) in good condition. 'Fare' itself comes from Old English 'faran' (to travel, to go), from Proto-Germanic *faraną, which is yet another derivative of PIE *per-. So 'farewell' is doubly connected to 'far': both words descend from the same root, and the compound encodes the act of departing to a distant place.
'Far-fetched,' now meaning 'implausible,' originally meant 'brought from far away' — a description of exotic goods imported from distant lands. The metaphorical shift from 'physically remote' to 'conceptually remote/unlikely' occurred during the sixteenth and seventeenth centuries. Similarly, 'far-flung' (widely distributed) and 'far-sighted' (able to see distant objects, or metaphorically, able to plan ahead) use 'far' as a productive combining form.
The word 'afar' (from a distance) preserves the Old English construction 'on feorr' (at a distance), with the preposition 'on' reduced to 'a-' as in 'ashore,' 'aside,' and 'asleep.' This archaic form survives mainly in literary and poetic contexts ('from afar,' 'gazing afar'), giving it a register distinctly more elevated than plain 'far.'
Phonologically, the development from Old English 'feorr' to Modern English 'far' involved the loss of the geminate (double) 'rr' and a vowel change from the Old English diphthong /eo/ to Middle English /e/ and finally to Modern English /ɑː/. The modern pronunciation with a long open vowel is characteristic of non-rhotic dialects (British RP), while rhotic dialects (American English) retain the final /ɹ/ as a consonant.