Correct spelling for the English word "Unpossible" is [ʌnpˈɒsəbə͡l], [ʌnpˈɒsəbəl], [ʌ_n_p_ˈɒ_s_ə_b_əl] (IPA phonetic alphabet).
"Unpossible" is not a commonly used English word. However, it seems to be a blend of the prefix "un-" meaning "not" or "opposite of" and the word "possible", which ultimately derives from the Latin word "possibilis". The prefix "un-" is of Germanic origin and has been used in English since ancient times to create words with negative or opposite meanings. It is possible that "unpossible" was created humorously or poetically to emphasize the impossibility or improbability of something.