ᴺS. !teleg n. “leg”
A Neo-Sindarin word for “leg”, derived from the root ᴹ√TELEK “stalk, stem, leg”.
Conceptual Development: There is an attested Gnomish word for “leg”, G. bactha (GL/21), but its form is not suitable for Sindarin. There is also a Quenya word for “leg” Q. telco appearing later writings, which also means “stem” (PE17/122, LotR/1118). This Quenya word appears in the Etymologies with the gloss “leg”, where its Noldorin equivalent is given as N. telch “stem” (Ety/TÉLEK). It’s possible this word could also mean “leg” in Sindarin, but Tolkien had the opportunity to give it this gloss and chose not to.
Perhaps the Primitive Elvish words were ✶téleku (or ✶telkwǝ) “stem” and ✶teléku (or ✶telékō) “leg”, with differing stress patterns. These two words would have blended in Quenya as telco, but would have remained distinct in Sindarin as telch “stem” and teleg “leg”. That’s the theory presented here.
Alternately, you might repurpose S. tâl “foot” to mean both “leg” and “foot” as happens in some real-world languages. This second option is partially supported by the word tad-dal “two-legged, *biped”, though the literal meaning of the word could actually be “*two-footed”.