severity (n.)

late 15c., "austerity or strictness of life," from Middle French severite, from Latin severitas "seriousness, strictness, sternness," from severus "stern, strict, serious," of uncertain origin, probably from PIE root *segh- "to have, hold," on the notion of "steadfastness, toughness." Meaning "strictness in dealing with others" is recorded from 1520s.