Interesting question/answer I found on Quora.
This is called a dogwhistle. A literal dogwhistle is a sound dogs can hear but humans can’t. A metaphorical dogwhistle is a coded message that one part of the audience understands and others do not. Or, as is more common in politics, everyone understands but some people can claim some shred of plausible deniability that it wasn’t meant that way.
Everyone on Donald Trump’s campaign knows that the six-pointed star is associated with Judaism.
This is the first time I’ve heard the term ‘dogwhistle’ used in this context.
I’m a sucker for great metaphors.