The word snapdragon derives from Antirrhinum, which is a genus of plants commonly known as snapdragons from the flowers' fancied resemblance to the face of a dragon that opens and closes its mouth when laterally squeezed, which as a result produces a snap-like sound.
For example, after 1♦ – 1♥ – 1♠, a double would show a hand with primary clubs and heart tolerance.
A typical hand for most partnerships would be ♠ Kxx ♥ Kx ♦ xx ♣ QJ10xxx.
An alternative modern interpretation is for this double to show "cards," and simply ask partner to do something intelligent.
Players choosing to make Snapdragon part of their partnership agreement should agree on: