Merriam-Webster Collegiate Dictionary - thou

 I. pronoun  Etymology: Middle English, from Old English thu; akin to Old High German du ~, Latin tu, Greek sy  Date: before 12th century archaic the one addressed ~ shalt have no other gods before me — Exodus 20:3(Authorized Version) — used especially in ecclesiastical or literary language and by Friends as the universal form of address to one person; compare thee, thine, thy, ye, you  II. transitive verb  Date: 15th century to address as ~  III. noun  (plural ~)  Etymology: short for ~sand  Date: 1867 a ~sand of something (as dollars) paid 25 ~ for the car