IRASCIBLE, meaning irritable or easily provoked, comes from Latin ira, as in Dies irae, "Day of Anger." How did the "-sc-" come into the picture? Second conjugation twice removed, or something like that?
I think I've mentioned it before. (Maybe not, I couldn't find a thread.) There's a verbal suffix, -sc-, for creating inchoative verbs in Latin. Rubesco 'to redden', irasco(r) 'to be angry, be in a rage'.