The American Heritage® Dictionary of the English Language: Fourth Edition. 2000.
Appendix I
Indo-European Roots
ENTRY:
tu-
DEFINITION:
Second person singular pronoun; you, thou. 1. Lengthened form *t (accusative *te,*tege). thee, thou1, from Old English th (accusative thec,th), thou, from Germanic *th (accusative *theke). 2. Suffixed extended form *t(w)ei-no-.thine, thy, from Old English thn, thine, from Germanic *thnaz. (Pokorny t 1097.)
(accusative *te, *tege). thee, thou1, from Old English th
), thou, from Germanic *th
n, thine, from Germanic *th
1097.) 
