Ilk. ado (adu-) adj. “double”
An adjective meaning “double” derived from the primitive root for two: ᴹ√AT (Ety/AT(AT)). The entry includes both intermediate and final forms adu and ado. Its Quenya cognate atwa indicates a primitive form *✶atwā, so this word is the clearest evidence that final [w] became [u] and final [u] became [o] in Ilkorin.
Reference ✧ Ety/AT(AT) ✧ “double”
|ᴹ√AT(AT) > adu > ado||[atwa] > [adwa] > [adw] > [adu] > [ado]||✧ Ety/AT(AT)|