Tenuous comes from Latin tenuis ('thin, slender, fine'), from Proto-Indo-European *tenh₂- ('to stretch'); the English form influenced by tenuity. The historical chain includes Latin tenuis and Proto-Indo-European *tenh₂-. The quoted older senses, "thin, slender, fine" and "to stretch", supply the semantic anchors for tenuous. The formation is best read as borrowed: the word tenuous carries its older form-history into a compact English lexical shape. In present English it is used as a adj, "very weak, slight, or insubstantial". English derivatives include tenuously and tenuousness; related English forms include tenuity, attenuate, and extenuate. The result is a adj whose etymology preserves both the older form and the later English specialization.