The name comes from the 0.618 ratio's association with the golden ratio. The pocket is a narrow band rather than a single line, which is at least more honest than pretending a level is exact.
Its popularity in crypto and forex is largely self-referential: a lot of traders watch it, so a lot of orders sit there. That can make it function as a level for reasons that have nothing to do with mathematics.
Be clear about what this is. A retracement of roughly two thirds is a deep pullback, and deep pullbacks in genuine trends are less common than shallow ones. Waiting for the golden pocket often means missing the trend entirely, and in a real reversal price sails straight through it.
Related: fibonacci-retracement, fibonacci-extension, pullback, self-fulfilling-prophecy, confluence