from The American Heritage® Dictionary of the English Language, 4th Edition
- adj. Chiefly British Slang Insane; mad.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. Plural form of cracker.
- adj. Crazy; mad.
from the GNU version of the Collaborative International Dictionary of English
- adj. crazy.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- adj. informal or slang terms for mentally irregular
Probably from cracker, breakdown.(American Heritage® Dictionary of the English Language, Fourth Edition)
From firecrackers in the head. Originally "He's got the crackers" then "He's gone crackers". Started as UK naval usage in the 1920's. (Wiktionary)