A word in a list of “large & small” roots from around 1968 glossed “stiff, wooden” and derived from the root √TAW “wood” (PE17/115). Its Sindarin cognate S. taug was gloss “firm, strong”, so its ancient sense was probably something like “stiff like wood”.
Quenya
tauca
stiff, wooden
tauca
adjective. stiff, wooden
norna
stiff, tough; hard, firm, resistant
norna adj. "stiff, tough; hard, firm, resistant" (WJ:413, PE17:106), "thrawn, tough, obdurate", mainly applied to persons (PE17:181)
tauca ("k") "stiff, wooden" (PE17:115)