anight comes from Middle English anight, from Old English on niht ('in the night'), from on ('in, at') + niht ('night'), from Proto-Germanic *nahts. Morphologically, the word is transparent as a compound: its parts remain visible in the modern spelling, while the older history of those parts supplies the deeper ancestry. In modern use, the adverb sense is "by night or in the night; nightly", which keeps the etymology connected to the word's present dictionary value rather than treating it as a merely historical label. The wider word family includes related English forms such as night, anights, showing how the same base continues to support neighboring English vocabulary. The principal historical forms in the chain include Old English on niht, Proto-Germanic *nahts, which anchor the explanation in named linguistic material.