Etymology From 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”).
1
Happening or appearing in the night; night-time; nocturnal.
nightly dews
A cobweb spread above a blossom Is sufficient to protect It from nightly chill.1871, John Tyndall, Fragments of Science: A Series of Detached Essays, Lectures, and Reviews:
2
Performing, occurring, or taking place every night.
The dog demanded to go out for his nightly walk.
3
Used in the night.
nightly
adv
Etymology From Middle English nyghtly, neghtly, from Old English *nihtlīċe (“nightly”), equivalent to night + -ly.
1
Every night.
He checks his email nightly.
It was the Nightingale, and not the Larke, / That pier'st the fearefull hollow of thine eare, / Nightly she sings on yond Pomgranet tree,c. 1591–1595 (date written), William Shakespeare, “The Tragedie of Romeo and Ivliet”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, →OCLC, [Act III, scene v]:
2 more examples
This tunnel assumed some measure of importance during the second world war, when it was used nightly as an air raid shelter for multiple unit electric trains which were propelled over the branch by a steam engine.1952 December, R. C. Riley, “By Rail to Kemp Town”, in Railway Magazine, page 836:
I practice nightly, I try to keep ahead / This art of surfacing is all but dead1979, The Boomtown Rats, “Wind Chill Factor (Minus Zero)”, in The Fine Art of Surfacing:
nightly
noun
Etymology From Middle English nyghtly, neghtly, from Old English *nihtlīċe (“nightly”), equivalent to night + -ly.
1
Computing, Engineering, Mathematics, Natural sciences, Physical sciences, Sciences, Software A build of a software program with the latest changes, released every night.
Depending on how brave you are, you can even set it to update to the “bleeding edge nightlies” instead of just the point release nightlies if you want to really see the cutting edge of WordPress core development.2014, Adam Onishi, Pro WordPress Theme Development, Apress, →ISBN, page 349: