Correct spelling for the English word "impiteous" is [ɪmpˈa͡ɪti͡əs], [ɪmpˈaɪtiəs], [ɪ_m_p_ˈaɪ_t_iə_s] (IPA phonetic alphabet).
There does not seem to be a widely recognized etymology for the word "impiteous". It is not listed in most English dictionaries or sources that specialize in etymology. It is possible that "impiteous" is a relatively rare or archaic word that has limited usage, making its origin or etymology difficult to trace.