A word for “sister” coined by Tolkien in notes on Eldarin Hands, Fingers and Numerals from the late 1960s, based on the root √NETH of similar meaning (VT47/12, 14). It had a diminutive/affectionate variant nettë used as a play name for the fourth finger in several places in these notes (VT47/12; VT48/6), but I prefer to mainly use nettë for “(little) girl” in Neo-Quenya (VT47/10, 15, 33).
Conceptual Development: The Etymologies of the 1930s had ᴹQ. seler “sister” from the root ᴹ√THEL or THELES (Ety/THEL), and the Qenya Lexicon of the 1910s had ᴱQ. heresse “sister” from the early root ᴱ√HESE (QL/40). See those entries for discussion.
*sistë* (sisti-) may be a possible phonological updating of the "Qenya" noun sist (sisty-) "ulcer". Adj. sistina** "ulcerated" (QL:86)