Dictionary — ontologydriven

mad as a March hare en · ADJ

Possibly from the boisterous behaviour of hares in their breeding season.

(informal, not-comparable, qualifier:simile) Crazy, demented.
- [S]he was with childe in hir huſbande his abſence, or that hir louer vſed hir fondly in open preſence, as the preſumption was not onely vehement, but alſo the fact too too apparent. Hir vnfortunat huſband had not ſooner notice gyuen him vpon his returne of theſe ſorowfull newes, then his fingers began to nibble, hys teeth to grinne, hys eyes to trickle, his eares to dindle, his heade to dezell, in ſomuch as his heart being ſkeared wyth ialouſie, & his wits enſtalde through Phrenſie, he became as madde, as a marche hare. 1577, Richard Stanyhurst [i.e., Richard Stanihurst], “[The Historie of Irelande […].] A Treatise Contayning a Playne and Perfect Description of Irelande, […].”, in Raphaell Holinshed, The Firste Volume of the Chronicles of England, Scotlande, and Irelande […], volume I, London: […] [Henry Bynneman] for Iohn Hunne, →OCLC, folio 14, recto, column 1:
- His nephew by marriage—his wife's own blood kin—had gone crackers and killed a man. […] When you added in the fact that the young man in question remained just as mad as a March hare, you could understand why the governor only wanted it to go away, and as soon as possible. 1996, Stephen King, The Green Mile: