As a reminder of or memorial to. For example, In memory of Grandma we put flowers on her grave every Easter, or In memory of our happy times here we've planted a little garden. [First half of 1300s]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.