Daily

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late Middle English: from day + -ly1, -ly2.

wiktionary

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From Middle English dayly, from Old English dæġlīċ, from Proto-Germanic *dagalīkaz(“daily”), equivalent to day +‎ -ly. Cognate with Scots dayly, daly(“daily”), German Low German dagelk, dagelik(“daily”), Dutch dagelijks(“daily”), German täglich(“daily”), Danish daglig(“daily”), Swedish daglig(“daily”), Icelandic daglegur(“daily”).

From Middle English dayly, from Old English *dæġlīċe (found only as dæġhwāmlīċe), equivalent to day +‎ -ly.

etymonline

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daily (adj.)

"happening or being every day," mid-15c.; see day + -ly (1). Compare Old English dglic, a form found in compounds: twadglic "happening once in two days," reodglic "happening once in three days." The more usual Old English adjective was dghwamlic (also dgehwelc), which became Middle English daiwhamlich. Cognate with German tglich.

As an adverb, "every day, day by day," early 15c. (the Old English adverb was dghwamlice. As a noun, "a daily newspaper," by 1832.