Correct spelling for the English word "adour" is [ɐdˈɜː], [ɐdˈɜː], [ɐ_d_ˈɜː] (IPA phonetic alphabet).
The word "Adour" is not of English etymology. It is a proper noun referring to a river in southwestern France. The name "Adour" is believed to have originated from the Gaulish word "ator" or "adur" which meant "watercourse" or "river". Over time, the name evolved and became "Adus" in Latin and eventually "Adour" in the French language.