Middle English lawar, lower, lougher, earlier lahre (c. 1200), comparative of lah "low" (see low (adj.)). As an adverb from 1540s. Lower-class is from 1772. Lower 48, "the forty-eight contiguous states of the United States of America, excluding Alaska and Hawaii," is by 1961 in an Alaska context (Hawaii actually is "lower" on the globe than all of them).
Old English niþera, neoþera "down, downwards, lower, below, beneath," from Proto-Germanic *nitheraz (source also of Old Saxon nithar, Old Norse niðr, which contributed to the English word, Old Frisian nither, Dutch neder, German nieder), from comparative of PIE *ni- "down, below" (source also of Sanskrit ni "down," nitaram "downward," Greek neiothen "from below," Old Church Slavonic nizŭ "low, down").
Also an adverb in Old English and Middle English. It has been replaced in most senses by lower (adj.). Of countries, "situated on lower ground" (late 14c.). In Middle English (and after) used also of body parts.
Absolon hath kist hir nether eye. [Chaucer, "Miller's Tale"]