Knew; to have known.

And when they saw him, they were amazed: and his mother said unto him, Son, why hast thou thus dealt with us? behold, thy father and I have sought thee sorrowing. And he said unto them, How is it that ye sought me? WIST ye not that I must be about my Father's business? ( Luke 2:48-49 )

Dictionary of Words from the King James Bible. Public Domain. Copy freely.