Correct spelling for the English word "downiest" is [dˈa͡ʊnɪəst], [dˈaʊnɪəst], [d_ˈaʊ_n_ɪ__ə_s_t] (IPA phonetic alphabet).
The word "downiest" is formed by adding the suffix "-iest" to the word "downy". The etymology of "downy" can be traced back to the Middle English word "doune", which meant "down" or "a covering of soft feathers". It originated from the Old English word "dūn" with the same meaning. The term "downy" itself refers to something that is covered in or resembles down, which is the soft, fine feathers found on young birds or certain plants.