ᴹ√THEL(ES) root. “sister”
Tolkien gave this root in The Etymologies of the 1930s as ᴹ√THEL and extended form ᴹ√THELES with the gloss “sister” and derivatives like ᴹQ. seler and N. thêl of the same meaning, both derived from the extended root as made clear by the Noldorin plural thelei < ON. thelehi (Ety/THEL). Hints of the roots continued use appear in the 1959 term Q. meletheldi “love-sisters” for close female friends (NM/20). In notes from the late 1960s, Tolkien gave Q. nésa and S. nethel as the words for “sister”, both from the root √NETH. Nevertheless, I think it is worth retaining ᴹ√THEL(ES) to represent more abstract notions of “sisterhood” for the purposes of Neo-Eldarin, for “metaphorical” sisters as opposed to Q. nésa/S. nethel for sisters by blood.
References ✧ Ety/THEL, TOR, WŌ