Emily Dickinson Lexicon

THOU, pron. [in the obj. Thee. Sax. thu; G. Sw. and Dan. du; L. Fr. It. Sp. Port. and Russ. tu; Sans. tuam. The nominative case is probably contracted, for in the oblique cases it is in Sw. and Dan. dig, in Goth. thuk, Sax. thec. So in Hindoo, tu in the nominative, makes in the dative, tuko; Gipsy, tu, tuke. In Russ. the verb is tukayu, to thou.]

The second personal pronoun, in the singular number; the pronoun which is used in addressing persons in the solemn style. Art thou he that should come? Matth. xi. I will fear no evil, for thou art with me. Ps. xxiii. Thou is used only in the solemn style, unless in very familiar language, and by the Quakers.