swine flu journals

Can someone tell me why it is named as swine flu?
I just don’t understand how the term swine has entered in the medical journals of humans.
http://healthmad.com/conditions-and-diseases/swine-flu-symptoms-that-doctors-never-tell-you/
the flu started in the pig and jumped to human. Kind of like the Bird Flu
CSPAN Swine Flu H1N1 call-in session: the jig is up! (Washington Journal)
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