bend sinister

noun2

1. •
   A diagonal band on a coat of arms going from the sinister chief (the viewer's top right) to the dexter base, sometimes erroneously held to indicate bastardy.
2. •
   (figurative, old-fashioned) Bastardy, (by extension) a defect or stigma.

   • A ‘bend sinister’ ran athwart his reputation as a priest. Men muttered that he was an infidel, a blasphemous vagabond, versed in all the damnable heresies of antiquity. — 1904