have bats in one's belfry

• have bats in the belfry

1899,[1] from tendency of bats to fly around erratically, with “belfry” indicating “head, mind”.

have bats in one's belfry

1. (idiomatic, intransitive) To be crazy or eccentric.

   Anyone declaring himself Emperor of San Francisco probably had bats in his belfry.

   • 1900, Mary Etta Stickney, Brown of Lost River, page 254:

     You would certainly take the prize for bats in the belfry!--flying off on a wild-goose chase across a country where even the geese need a compass to keep to the course.

• See also Thesaurus:insane

• batshit
• batty