The American Heritage® Dictionary of the English Language: Fourth Edition. 2000.
Appendix I
Indo-European Roots
ENTRY:
agh-
DEFINITION:
A day (considered as a span of time). Oldest form *ah-, becoming *agh- in centum languages. a.day; daisy, today, from Old English dæg, day; b.Landtag, from Old High German tag, day; c.dawn, from Old English denominative dagian, to dawn. a–c all from Germanic *dagaz (with initial d- of obscure origin), day. (Pokorny her- 7.)
h-, becoming *agh- in centum languages. a. day; daisy, today, from Old English dæg, day; b. Landtag, from Old High German tag, day; c. dawn, from Old English denominative dagian, to dawn. a–c all from Germanic *dagaz (with initial d- of obscure origin), day. (Pokorny 
