In the Etymologies, the word for “craftsman, smith” was ᴹQ. tano, N. *tân as in N. Cirdan “Shipbuilder”, both from the root ᴹ√TAN “make, fashion”. In later writings, Tolkien changed √TAN >> √TAM “construct” and the Quenya form tano >> tamo “smith” (PE17/107-108), possibly due to conflict with a new root √TAN² “show, indicate”. That this change was lasting is supported by the appearance of the form Q. Martamo as a title of Aulë in a “very late note” (LT1A/Talka Marda), as opposed to the form ᴹQ. Martan(o) in the Etymologies (Ety/TAN).
However, √TAM would have produced S. *tav, and Tolkien wanted to retain the name Círdan. On PE17/108, he indicated that √TAN became the usual Sindarin form of the root, owing to the influence of √PAN “arrange, set in order”. Thus, the Sindarin development would have been √TAM > ✶tan- > tân, lenited in S. Círdan and S. calardan “lampwright”, whose plural appears in The Lord of the Rings as part of S. Rath Celerdain “Lampwrights’ Street”.
In The Etymologies, the word for “craftsman, smith” was ᴹQ. tano, N. *tân as in N. Cirdan “Shipbuilder”, both from the root ᴹ√TAN “make, fashion”. In later writings, Tolkien changed √TAN >> √TAM “construct” and the Quenya form tano >> tamo “smith” (PE17/107-108), possibly due to conflict with a new root √TAN “show, indicate”. That this change was lasting is supported by the appearance of the form Q. Martamo as a title of Aulë in a “very late note” (LT1A/Talka Marda), as opposed to the form ᴹQ. Martan(o) in The Etymologies (Ety/TAN).
However, √TAM would have produced S. tav, and Tolkien wanted to retain the name Círdan. On PE17/108, he indicated that √TAN became the usual Sindarin form of the root, owing to the influence of √PAN “arrange, set in order”. Thus, the Sindarin development would have been √TAM > ✶tan- > tân, lenited in S. Círdan and S. calardan “lampwright”, whose plural appears in The Lord of the Rings as part of S. Rath Celerdain* “Lampwrights’ Street”.