An element in the name Q. Avallónë “Outer Isle”, thus likely “[remote] isle”.
Conceptual Development: A similar form ᴹQ. lóna “island, remote land difficult to reach” appeared in The Etymologies of the 1930s as the only derivative of the root ᴹ√LONO (Ety/LONO). This root was connected to the ablative element ᴹ√LŌ “✱from” (EtyAC/LŌ, LONO), so “remote land” is likely the original meaning. This word lóna was an element of the name ᴹQ. Avalóna “Outer Isle”, which ultimately became Q. Avallónë (S/260), a name that Tolkien said was “signifying the isle that lies nighest unto the Valar in Valinor” (MR/175 footnote). Thus lónë appears to be an updated version of ᴹQ. lóna, probably of similar meaning.
tol noun "island, isle" (rising with sheer sides from the sea or from the river, SA:tol, VT47:26). In early "Qenya", the word was defined as "island, any rise standing alone in water, plain of green, etc" (LT1:269). The stem is toll-; the Etymologies as published in LR gives the pl. "tolle" (TOL2), but this is a misreading for tolli (see VT46:19 and compare LT1:85). The primitive form of tol is variously cited as ¤tolla (VT47:26) and ¤tollo (TOL2).