Quadruple Witching

Those days are the expiration of three kinds of securities:
Stock index futures.
Stock market index options.
Stock options.
The simultaneous expirations generally increases the trading volume of options, futures and the underlying stocks, and occasionally increases volatility of prices of related securities.
With the introduction of
Single stock futures expiring on the same days, triple witching has become quadruple witching



Concept
The term "triple witching" is conventionally thought to originate from the three witches in Shakespeare's play Macbeth. While the terms "double witching" and "quadruple witching" are sometimes used too, it doesn't carry the same foreboding connotation as triple witching.