frailty (n.)

late 14c., "moral weakness," from Old French fragilité "debility, frailty" (12c.), from Latin fragilitatem (nominative fragilitas) "brittleness, weakness," from fragilis "brittle, easily broken," from root of frangere "to break" (from PIE root *bhreg- "to break"). Meaning "quality of being easily broken" is from late 15c.