An island at the mouth of the Anduin appearing on the maps of The Lord of the Rings (LotR/1185), a combination of tol(l) “island” and falas “shore”.
Conceptual Development: This island also appeared in draft maps for the Lord of the Rings (TI/298), but not appear in the main text.
The most common Sindarin word for “island”, strictly speaking only for islands with sheer sides as opposed to [N.] caer for flat islands. It was a derivative of the root √TOL “stick up or out, stand up (out and above neighboring things)” (VT47/10-11). In most names it appears as tol, probably as a semi-prefix, but as an independent word it is probably toll (Ety/TOL), especially given its Quenya cognate Q. tollë (VT47/13, 28).
Conceptual Development: This word dates all the way back to the Gnomish Lexicon of the 1910s where it appeared as G. tol “an isle (with high steep coasts)” (GL/71), probably already a derivative of the root ᴱ√TOLO as suggested by Christopher Tolkien (LT1A/Tol Eressëa; QL/94). In Early Noldorin Word-lists of the 1920s it appeared as ᴱN. dol “island” (PE13/142), but that seems to have been a transient idea since it was N. toll “island” in The Etymologies of the 1930, again derived from the root ᴹ√TOL, more specifically from the primitive form ᴹ✶tollo (Ety/TOL²). The form tol appeared regularly in Tolkien’s later writings, and in several places he emphasized that it was for islands with steep sides (RC/333; VT47/28).