from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. Demented or crazy.
Disputed. Possibly from Old English ātor ("poison"), and thus related to English atter. Alternatively from hat-makers suffering from Korsakoff's syndrome due to handling mercury-contaminated felt. (Wiktionary)
"We can't have Esme pawning her off on some unsuspecting fellow and discover she's mad as a hatter and poisoned two previous husbands before her arrival here."