Green’s Dictionary of Slang

beno n.

[‘there’ll be no fun’; note WWII USN beeno, there will beeno moving pictures tonight etc]

the period of menstruation and thus, for many couples, no sex.

Show quotations
[US] ‘Miscellany’ AS XXIX:4 298: Reference to Material Culture [...] Beno (M[en]; short for ‘There’ll be no fun’).