The word 'under' descends directly from the Old English preposition 'under', which carried the same core spatial meaning of 'beneath' or 'among'. This Old English term finds its source in Proto-Germanic under-, which in turn is derived from the Proto-Indo-European root ndher-, meaning 'under'. This ancient root is also the ancestor of related terms in other languages, such as Sanskrit 'adhas', Latin 'infra', and Greek 'hypo'. The semantic journey of 'under' is remarkably stable, maintaining its fundamental sense of relative lower position from its prehistoric origins through to its modern abstract uses denoting lesser rank, degree, or amount.

The word 'under' is a simplex word of Old English origin. It functions as a core preposition and adverb in English.