Just as without was once commonly used to mean on the outside, so within was once commonly used to mean on the inside (and still largely is). This is a verse from the New Testament of the bible, from the book of Matthew, Chapter 23:
Quote:Woe unto you, scribes and Pharisees, hypocrites! for ye are like unto whited sepulchres, which indeed appear beautiful outward, but are within full of dead men's bones, and of all uncleanness.
Within here means on the inside.