(adj.) extremely criminal, guilty of terrible crimes
Today’s Word of the Day on HH is a good one: if you’re flagitious, then you’re guilty of atrocious crimes.
Dating back to the Middle English period in English (but rarely used since the nineteenth century), flagitious derives via French from its Latin equivalent, flagitiosus. That word in turn comes from flagitium, a Latin word for a crime, an instance of importunity, or any equally shameful act.
Flagitium itself comes from flagitare, a Latin verb literally meaning “to demand,” or “to entreat.” How that came to be connected with shamefulness is unclear: it could be that a sense emerged later of rudely demanding or entreating something, which in polite society would obviously be frowned upon, or else there could be a criminal connection to the later use of flagitare to mean “to accuse.”
Either way, somehow that verb came to be associated with bad behaviour, disgrace, and ultimately heinous acts and crimes. And it’s in that sense that the word was first imported into English in the fourteenth century.