The most common Quenya word for isle or island, appearing in both a short form tol (toll-) and longer form tolle, an element in many names. Strictly speaking it only “applied to those [islands] that rose up from the water with sudden and sheer sides” (VT47/28), but in practice it seems to have been used for all kinds of islands. Its short form tol was used as pseudo-prefix in names (VT47/13, 28) such as Tol Eressëa and Tol Uinen, and thus in more ordinary phrases its longer form tolle is more likely.
Conceptual Development: This word dates all the way back to the Qenya Lexicon of the 1910s where ᴱQ. tol (toll-) appeared with the gloss “an island, any rise standing alone in water, plain of grass, etc.” derived from the root ᴱ√TOLO (GL/94). It appeared as toll- “isle” in the Poetic and Mythological Words of Eldarissa (PME/94) and as tolle “island” in Early Qenya Word-lists of the 1920s beside its shorter form tol (PE16/139).
In The Etymologies of the 1930s it appeared as ᴹQ. tol “island” as a derivative of primitive ᴹ✶tollo (Ety/TOL²). It appeared several times in notes on Eldarin Hands, Fingers and Numerals from the late 1960s, in one place as short tol < ✶tollă (VT47/26 note #35), but Tolkien gave a more complete description in the final version of these documents:
> TOL “stand up (out and above neighbouring things)” ... A frequent topographical application was to islands that rose up from the water (sea or river) with sheer sides ... Cf. Q. tolle “a steep isle”. This was used in form Tol- as a prefix to the isle’s name: as in Tol-eressea (VT47/10 and p. 13 note #14).
tollë noun "a steep isle". Another meaning, "thumb", was apparently abandoned by Tolkien (VT47:13, 26)