I think the horrid creature meaning and the sample meaning are cognates (both from Latin for 'show', in one case because the sample is made for purposes of show

I think the horrid creature meaning and the sample meaning are cognates (both from Latin for 'show', in one case because the sample is made for purposes of showing it to someone, and in the other case because you can't look away, so to speak). (Or because the gods wanted to show you that they were displeased with you, maybe.)