Would-be white people who are not from Ireland with African heritage (and in at least one case, Iranian, which generally includes African somewhere in that heritage) also were/are referred to as Black Irish, Black Dutch, etc to explain the darker skin..
In fact, I know someone personally who had a child with an Iranian but was not married to him, ever, and explained the child's darker skin as being from having Black Dutch ancestry...There was no Dutch in the ancestry..
People say things to *explain away* certain things to white people who might treat them differently if they admit their actual heritage..
Silly world, isn't it?