What's the difference between i.e. and e.g.?
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. Possibly from PIE root *segh- "to have, hold" (see scheme (n.)), or possibly from *se vero "without kindness," from se "without" (see secret) + *vero "kindness," neuter ablative of verus "true" (see very). Meaning "strictness in dealing with others" is recorded from 1520s.