"principle," properly "a thing held (to be true)," 1413, from L. tenet "he holds," third person singular present indicative of tenere "to hold, to keep, to maintain" from PIE base *ten- "to stretch" (cf. Skt. tantram "loom," tanoti "stretches, lasts;" Pers. tar "string;" Lith. tankus "compact," i.e. "tightened;" Gk. teinein "to stretch," tasis "a stretching, tension," tenos "sinew," tetanos "stiff, rigid," tonos "string," hence "sound, pitch;" L. tendere "to stretch," tenuis "thin, rare, fine;" O.C.S. tento "cord;" O.E. thynne "thin"). Connection notion between "stretch" and "hold" is "to cause to maintain." The modern sense is probably because tenet was used in M.L. to introduce a statement of doctrine.