haneyin sin noun a wicked, cruel, unforgiveable sin: ‘I don’t know how how you could do that to the poor wee creatures [catch trout], that is a haneyin sin ...’ ‘Aye but it’s not a sin to eat them ...’ 20-. etymology: perhaps the first element is a development from English heinous ‘Hateful, odious; highly criminal or wicked; infamous, atrocious: chiefly characterizing offences, crimes, sins, and those who commit them’ + English sin; attested by BW