What's the difference between i.e. and e.g.?
Old English fæstnian "make fast, firm," also "ratify, betroth," from Proto-Germanic *fastinojanan (cf. Old Frisian festnia "to make firm, bind fast," Old Saxon fastnon, Old High German fastnion, Old Norse fastna "to pledge, betroth"), from *fastuz (see fast (adj.)). Related: Fastened; fastener; fastening.