either

The word 'either' originates from the Old English 'ǣgther', a contracted form of 'ǣghwæther', which itself was a combination of 'ǣg' (a variant of 'ā', meaning 'ever' or 'always') and 'gehwæðer' (meaning 'each of two, which of two'). This Proto-Germanic root, related to Old High German 'eogihwedar' and Old Norse 'hvárr', essentially meant 'each of two'. The semantic journey moved from a sense of 'each of two' or 'both' to its primary modern function of presenting a choice between two alternatives. The shift in pronunciation, with the UK variant /ˈaɪðə(r)/ and the US variant /ˈiːðər/, reflects different paths in the Great Vowel Shift and subsequent dialectal developments.

The word 'either' is a simplex form derived from Old English. It is a fusion of the Old English elements 'ǣg' (ever, always) and 'gehwæðer' (each of two, both). It does not neatly divide into meaningful substrings in its modern English spelling.