Also, a
festival at
Argos in which
swine were
sacrificed to
Aphrodite.
From the Greek hys 'pig' (that kind of swine... not the kind who leave orange-juice stains in library books or downvote your nodes), with a pun on mystery, the more usual kind of Greek festival.
It is not recorded what Aphrodite did with all the dead swine. In fact, the more I think about it, the less I want to know.