A noun appearing as G. tadhos “hawthorn” in the Gnomish Lexicon of the 1910s, an elaboration of G. tath (tadh-) “hedge” based on the early root ᴱ√tadh- (GL/68).
Neo-Sindarin: I would retain ᴺS. tadhos “hawthorn” based on an updated Neo-Root ᴺ√TAD “enclosure”; see that entry for details.
A word for “hawthorn” in the Gnomish Lexicon of the 1910s, apparently a combination of G. pibin “small berry, haw” and a variant of G. aithos “thorn bush” (GL/64). Another word of “hawthorn” in this document was G. tadhos (GL/68).