A "philter" (FIL-tur) is a love potion or charm. It is derived from the Greek for "to love."
Example (as used by Umberto Eco in Foucault’s Pendulum): "Some things you can feel coming. You don’t fall in love because you fall in love; you fall in love because of the need, desperate, to fall in love. When you feel that need, you have to watch your step; like having drunk a philter, the kind that makes you fall in love with the first thing you meet. It could be a duck-billed platypus."
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