The same quantity as. As with as many (def. 2), the meaning of much as a large amount here is qualified by what follows. For example, Please help yourself to as much of the meant as you want indicates whatever amount you wish. [Late 1100s]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.