√THOL root. “stand up, top; helmet”
In Quenya Notes (QN) from 1957 Tolkien gave the root √STOL “helmet” with derivatives like S. thôl or Q. castol of the same meaning (PE17/186). In etymological notes from around 1964 (DD) Tolkien instead gave √ÞOL “stand up, top” as the basis for these “helmet” words (PE17/188).
References ✧ PE17/145, 186, 188