Meaning

adjective happening every night

adverb at the end of each day

originFrom Middle English nyȝtly, nihtlich, nihtlic, from Old English nihtlīċ, nihtelīċ (“nocturnal, nightly, of the night, at night”), equivalent to night + -ly. Cognate with Scots nichtlie (“nightly”), West Frisian nachtlik (“nightly, nocturnal”), Dutch nachtelijk (“nightly, nocturnal”), German nächtlich (“nocturnal, nightly”), Danish natlig (“nightly”), Swedish nattlig (“nightly, nocturnal”).

Etymology from Wiktionary, CC BY-SA 3.0