A noun in The Etymologies of the 1930s glossed “shell, conch, horn of Ulmo” derived from primitive ᴹ✶syalmā under the root ᴹ√SYAL (Ety/SYAL). In this document hyalma was given as the name of tengwa #33 (9), and it appeared again as the name of this tengwa in notes on The Feanorian Alphabet from the 1930s (PE22/22) and 1940s (PE22/51) with the glosses “conch” and “conch, shell” respectively. In the 1940s document, hyarmen “south” was given as an alternate name of the tengwa, and hyarmen was the name Tolkien used in The Lord of the Rings proper.
Quenya
hyalma
shell, conch, horn of ulmo
hyalma noun "shell, conch, horn of Ulmo" (SYAL). In the pre-classical Tengwar system presupposed in the Etymologies, hyalma was also the name of tengwa #33 (VT46:16), which letter Tolkien would later call hyarmen instead.