"like freemasons, any common sign of communication"

Freemasonry arose in the late 16th to early 17th century. The fraternity is organised into independent Grand Lodges, which preside over subordinate or constituent Lodges. The various Grand Lodges recognise each other based upon adherence to common principles, known as landmarks

Freemasons use secret signs, grips or handshakes and words to gain admission to meetings and identify legitimate visitors.  Each Grand Lodge is free to create its own rituals, so the identifying signs, grips and passwords differ across jurisdictions.