2020-03-09 Oops, I confused perfid- and impi- again.
"perfidias" think "perfidy" (in English).
"Perfidy" refers to a traitorous action (such as rioting in the capital to stop a peaceful transfer of power, as recently happened in the country of Samoa).
perfidus, -a: treacherous, disloyal, traitor.
ignavus, -a: lazy, indolent.
I hope we also fo not teach deceitful boys.