An element in the Entish word Q. sincahonda “flint-hearted” (LotR/979), and thus apparently a noun and/or adjective “flint” or “✱flinty”. In a note from the 1968 Tolkien said “Sincahonda referred to their [Orcs] immense staying power in exertion, marching, running, or climbing, which gave rise to the jesting assertion that their hearts must have been made of some exceedingly hard substance; it did not mean pitiless (NM/176)”, so possibly sinca simply referred to any hard or stone-like substance.
Conceptual Development: In the Qenya Lexicon of the 1910s Tolkien had an adjective ᴱQ. siliq(in)a “flinty” and a noun ᴱQ. silik (siliq-) “flint” under the root ᴱ√SILI, though marked with a “?” indicating Tolkien was uncertain of its derivation (QL/83). silik “flint” also appeared in the contemporaneous Poetic and Mythological Words of Eldarissa (PME/83). In Lord of the Rings drafts from the 1940s, “flint-hearted” was first given as ᴹQ. tingahondo (SD/68), with ᴹQ. tinga “flint” probably a variant of ᴹQ. tinko “metal” (Ety/TINKŌ). I think Q. sinca is probably a later variant of the early word ᴱQ. sink (sinq-) “mineral, metal, gem” from the 1910s (QL/83); see that entry for discussion.
An element in the Entish word Q. sincahonda “flint-hearted” (LotR/979), and thus apparently a noun and/or adjective “flint” or “✱flinty”. In a note from the 1968 Tolkien said “Sincahonda referred to their [Orcs] immense staying power in exertion, marching, running, or climbing, which gave rise to the jesting assertion that their hearts must have been made of some exceedingly hard substance; it did not mean pitiless (NM/176)”, so possibly sinca simply referred to any hard or stone-like substance.
Conceptual Development: In the Qenya Lexicon of the 1910s Tolkien had an adjective ᴱQ. siliq(in)a “flinty” and a noun ᴱQ. silik (siliq-) “flint” under the root ᴱ√SILI, though marked with a “?” indicating Tolkien was uncertain of its derivation (QL/83). silik “flint” also appeared in the contemporaneous Poetic and Mythological Words of Eldarissa (PME/83). In Lord of the Rings drafts from the 1940s, “flint-hearted” was first given as ᴹQ. tingahondo (SD/68), with ᴹQ. tinga “flint” probably a variant of ᴹQ. tinko “metal” (Ety/TINKŌ). I think Q. sinca is probably a later variant of the early word ᴱQ. sink (sinq-) “mineral, metal, gem” from the 1910s (QL/83); see that entry for discussion.