Infrangible comes to us via Middle French from the Late Latin infrangibilis and is ultimately derived from the prefix in- and the Latin verb frangere, meaning "to break." (Believe it or not, our "break" is ultimately derived from the same ancient word that gave rise to "frangere.") "Infrangible" first appeared in print in English in the 16th century with the literal meaning "impossible to break"; it was later extended metaphorically to things that cannot or should not be broken.