femfemma

Etymology
From, roughly "five-fiver." Attested since the 1940s.

Noun

 * 1)  a person declared not guilty by reason of insanity according to section 5 of chapter 5 of the Swedish Penal Code of 1864 (replaced in 1965)
 * 2)  an idiot, a crazy
 * 3) a 5.5 Metre (keelboat)