The spelling of the surname "McKeithan" can be confusing due to the use of the "Mc" prefix and the combination of letters "ei". However, using the International Phonetic Alphabet (IPA), the pronunciation of "McKeithan" becomes clearer. "Mc" is pronounced as /mək/, while "ei" sounds like /eɪ/. The final syllable "than" is pronounced as /θən/. Therefore, the correct pronunciation of "McKeithan" is /məkˈeɪθən/. Remembering the sounds associated with each letter or combination can make spelling and pronunciation easier.