The spelling of the surname "McMullen" can be explained using the International Phonetic Alphabet (IPA). The first syllable is pronounced as "mək" with a neutral vowel sound (schwa), followed by the voiced consonant "m". The second syllable starts with the voiceless consonant "k", followed by the vowel "ʌ". The last syllable ends with the voiced consonant "l", followed by the neutral vowel sound "ən". Together, the IPA transcription for "McMullen" is /məkˈmʌlən/.
The word "McMullen" is a Scottish and Irish surname of Gaelic origin. It is an anglicized form of the Gaelic name "Mac Maoláin", meaning "son of Maoláin". The Gaelic personal name "Maoláin" derives from the word "maol", which means "bald" or "tonsure". This name was often given to individuals who had a distinctive tonsure or a bald head. "Mac Maoláin" eventually evolved into "McMullen" when the name bearers migrated to English-speaking regions and their name was anglicized.