GARRISON, originally a term for stores or supplies, also a defence or protection, now confined in meaning to a body of troops stationed in a town or fortress for the purpose of defence. In form the word is derived from O. Fr. garison, modern guérison, from guérir, to furnish with stores, to preserve, but in its later meaning it has been confused with the Fr. garnison, the regular word for troops stationed for purposes of defence. In English "garnison" was used till the 16th century, when "garrison" took its place. In the British army "garrison troops," especially "garrison artillery," are troops trained and employed for garrison work as distinct from field operations.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)