I. ˈthīn adjective
Etymology: Middle English thin, from Old English thīn
Date: before 12th century
archaic : thy — used especially before a word beginning with a vowel or h
II. pronoun, singular or plural in construction
Etymology: Middle English thin, from Old English thīn, from thīn thy — more at thy
Date: before 12th century
archaic : that which belongs to thee — used without a following noun as a pronoun equivalent in meaning to the adjective thy ; used especially in ecclesiastical or literary language and still surviving in the speech of Friends especially among themselves