The name Garrison is a boy's name of English origin meaning "son of Garret". Garrison and is often added to lists like Names with Military Meanings and discussed in our forums with posts like "A Duggarlike Game: With a twist!".
From the experts:
As Harrison is to Harry, Garrison is to Gary: both of the longer versions sound more modern and appealing. NPR's Prairie Home Companion's Garrison Keillor was born Gary.