Unknown, perhaps originally Dublin slang. According to Green’s Dictionary of Slang, may be a euphemism for bollocks.
Meanings
(UK, slang) To ruin or destroy.
Emma had suggested that you hide, said your presence might banjax her position. 1970, Edna O'Brien, A Pagan Place, Houghton Mifflin Harcourt, published 2001, page 91:
For quotations using this term, see Citations:banjax.
Indeed, it seemed that the army was hopelessly banjaxed. 1928, Eimar O'Duffy, The Spacious Adventures of the Man in the Street, Macmillan, page 370:
Fraser was looking at the flat, wet countryside and thinking about the French policeman who had banjaxed him with the truncheon. 2006, Craig Ferguson, Between the Bridge and the River, Chronicle Books, page 252:
I hoofed his backside till he went down all of a heap. That banjaxed his little game. You should have heard his hullabulloo. 1922, Darrell Figgis, The House of Success, The Gael Co-operative Publishing Society, Ltd., page 146:
Forms
Spelling
Features
Labels
Source
banjaxed
Tense=Past, VerbForm=Part
lexicographic
banjaxed
Tense=Past
lexicographic
banjack
alternative
lexicographic
bandjax
alternative
lexicographic
banjaxes
Number=Sing, Person=3, Tense=Pres
lexicographic
banjaxing
Tense=Pres, VerbForm=Part
lexicographic
Translations (7)
de ruinieren (To ruin or destroy) · tpi bagarapim (To ruin or destroy) · de zerstören (To ruin or destroy) · it rovinare (To ruin or destroy) · it distruggere (To ruin or destroy) · fr ruiner (To ruin or destroy) · fr détruire (To ruin or destroy)