merged from 14c.; the distinction between them passed out of general usage by 1600. Widespread use of Fr. in England after 12c. gave Eng. you the same association as Fr. vous, and it began to drive out sing. nom. thou, originally as a sign of respect (similar to the "royal we") when addressing superiors, then equals and strangers, and ultimately (by c.1575) becoming the general form of address. For a more thorough discussion of this, go here
. Words for "you" in Japanese include anata (formal, used by a wife when addressing her husband), kimi (intimate, used among friends) or the rougher omae (oh-MAI-aye), used when talking down to someone or among male friend showing their manliness. Dial. you-uns, for you-ones, first noted 1810 in Ohio.
"Children learn from the slaves some odd phrases ... as ... will you all do this? for, will one of you do this?" ["Arthur Singleton" (Henry C. Knight), "Letters from the South and West," 1824]