Definition from Wiktionary, the free dictionary
Alternative forms 
Probably from Mandinka maamajomboo (“mask; masked dancer”). What might be possible as well is the occurance of l-vocalization in the words "mumble" and "jumble".
- IPA: /mʌmbəʊˈdʒʌmbəʊ/
mumbo jumbo (uncountable)
- (historical) A deity or other supernatural being said to have been worshipped by certain West African peoples; an idol.
- (religion) Any object of superstition; religious words and/or actions which are seen as superstitious or fraudulent.
- Rev. Quack's healing services are little more than mumbo jumbo.
- Any confusing or meaningless speech; nonsense, gibberish.
- Football lingo is mumbo jumbo to me.
- There were a bunch of foreigners speaking their Mumbo Jumbo clustered ahead of me at Customs.