I believe the name was coined for their "resemblance" to a bruised banana. Obviously some are more bruised
Anyway, that used to be my take and I haven't ever really looked into it further. Some I have had were very dark brown (black) and yellow. While it may well be a natural occurrance in the wild, probably most were man-made when crossing different patterns and colors. The "coastal" line seems to maybe be the founding stock??
Just my very humble opinion.
Surely someone here has the real low-down....
:Mark
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Surrender Dorothy!

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