So Wikipedia attributes the origin of the word “banana” to the Wolof (west African language, spoken in modern Sénégal) word banaana, however I learned a different version of events from my Arabic tutor yesterday.
She explained that while the current word for finger in Arabic is asb’a3, the classical arabic word was banan. While the word for banana in modern Arabic is al-mauz, this is actually a plural word in Arabic. The proper word for a single banana was banan al-mauz, or a finger of bananas. (For any Arabic students/grammar nerds out there, yes this is an idaafa).