A noun appearing as N. othlon “paved way” in The Etymologies of the 1930s, a combination of N. ost “city” and N. lhonn “path” (Ety/LOD), where medial str > sr > th and final -nd > -nn > -n in Noldorin/Sindarin.

Neo-Sindarin: Some Neo-Sindarin writers update this as ᴺS. othlonn “paved way”, as suggested in Hiswelókë’s Sindarin Dictionary (HSD). Tolkien himself was inconsistent in using final -nn vs. -n, and for a time in the 2000s Neo-Sindarin writers used -nn in two-syllable words and -n only in words of three syllables or longer. Personally I would just stick with othlon.

The meaning of this word is also somewhat questionable. N. lhonn meant “path, pass” in the 1930s (vs. N. lhorn “haven = harbour”), but by the 1950s and 60s Tolkien used its successor S. lond almost exclusively to mean “haven = harbour”. Personally I would keep using othlon “paved way”, and assume some amount of semantic drift.