The spelling of the surname "McGaha" can be explained using IPA phonetic transcription. The "Mc" prefix is pronounced as "mɑk", while the "G" and "H" in "Gaha" are pronounced separately as "ɡ" and "h". The vowel sound in the second syllable is an "a" pronounced as "ə". Finally, the last syllable is pronounced as "hɑ" with a silent "G". Therefore, the correct spelling of the surname is "McGaha" pronounced as "mɑk-ɡə-hɑ". Phonetic transcription helps to better understand the pronunciation of words and names.