An Etymological Dictionary of the German Language/Annotated/Tag

by Friedrich Kluge

Tag, masculine, ‘day, daylight,’ from the equivalent Middle High German and Old High German tac (g), masculine; common to Teutonic in the form dago-; compare Gothic dags, Old Icelandic dagr, Anglo-Saxon dœg, English day (also to dawn), Dutch and Old Saxon dag. This specifically Teutonic word represents the stem, almost obsolete in Teutonic, of the equivalent Latin dies, Sanscrit dina, Old Slovenian dī̆nī̆ (Gothic sin-teins, ‘daily,’ see Sündflut). To explain Teutonic dago- (to which Anglo-Saxon dôgor, Old Icelandic dœ́gr, from dôgoz, dôgiz, are allied), it has been connected with the Sanscrit root dah (for Aryan dhē̆gh, dhō̆gh?), ‘to burn’; this appears further in Lithuanian dègti, ‘to burn,’ dágas, dagà, ‘harvest’ (also in Sanscrit áhar, neuter, ‘day’?). Hence the base dhógho-s, common to German Tag and Lithuanian dágas, means perhaps ‘the hot period of the day or year’ (compare Ostern as a proof that names for periods of the day and year may be identical). Tag in German denoted originally only the light period of the day; the day of twenty-four hours was called Nacht. —