Meaning of word 'MADEO'

The English pronunciation of the word "mother" cannot be written or said correctly using the Korean language. So, "madeo" is the Korean pronunciation of the English word "mother". Even though it's written as "madeo", you should think of it more like "maduh". If you say it to yourself you will understand. This type of borrowed word in the Korean language is called Konglish.

It's the way the english word "mother" sounds when spoken by a korean person. It would sound more like "mah-duh." Interestingly, a korean person's pronunciation of the word "murder" would be similar ('muh-duhr"). It's brilliant. By not using the actual korean word for mother in the title, you get this ironic play on words. Another one of the director's clever details.