Thousand
A 'thousand' means much, many, a countless number, a whole era of time, an abundance. When used in reference to the Lord, it actually means a number greater than that: In those cases it means what is infinite, what is truly without end.
Medicine
In Ezekiel 47:12, the leaf represents intelligence for the celestial man and is called 'medicine.'
(References: Arcana Coelestia 57)