pronoun
you (dated, to equals or inferiors)
Dated second-person pronoun used toward equals or those of lower status. Now mostly encountered in historical or period speech; in modern Japanese it sounds old-fashioned or theatrical.
See also: 主 (ぬし)
「お主も悪よのう」と時代劇の悪代官が言った。
"You're a bad one too," said the corrupt magistrate in the period drama.
お主、なかなかやるな。
You're pretty good, aren't you? (archaic flavor)
Combination of the honorific prefix お and 主 (ぬし, 'master' or 'you'), an old second-person pronoun. The exact historical development is uncertain, but it was used in the Edo period and later.