O.E.
dæg, from P.Gmc.
*dagaz, from PIE
*dhegh-. Not considered to be related to L.
dies (see
diurnal), but rather to Skt.
dah "to burn," Lith.
dagas "hot season," O.Prus.
dagis "summer." Meaning originally, in Eng., "the daylight hours," expanded to mean "the 24-hour period" in late O.E.
Daydream is 1685 (n.), 1820 (v.).
Day off first recorded 1883;
day-tripper first recorded 1897;
daylight in slang sense of "clear open space between two things" is from 1820.
Day-Glo is 1951, proprietary name (Dane & Co. of London) for a brand of fluorescent paint. The
days in
nowadays, etc. is a relic of the O.E. and M.E. use of the adverbial genitive.
[dey] 
ərd