Where does “Flying Banana” come from?

Flying Banana (English) comes from English banana, from Spanish banana, from Portuguese banana, from Wolof banaana — banana.

Flying Banana (English): The New Measurement Train; the high-speed track testing train used on the British railway network

Definitions

The New Measurement Train; the high-speed track testing train used on the British railway network

Flying Banana traces back through two separate lines of ancestry.

Step	Language	Word	Meaning
1	English	banana	An elongated curved tropical fruit that grows in...
2	Spanish	banana	banana fruit
3	Portuguese	banana	banana; penis; bras d'honneur
4	Wolof	banaana	banana

Step	Language	Word	Meaning
1	English	flying	That flies or can fly; Brief or hurried; Not...
2	Middle English	flyinge	—