perfidy
noun /ˈpɜːfədi/
/ˈpɜːrfədi/
[uncountable] (literary)- unfair treatment of somebody who trusts you synonym treachery
- In Act 2 he learns of Giovanni’s perfidy and swears revenge.
Word Originlate 16th cent.: via French from Latin perfidia, from perfidus ‘treacherous’, based on per- ‘to ill effect’ + fides ‘faith’.