The jersey number 1 is globally recognized as the number of the starting goalkeeper. A football team's goalkeeping trio is often referred to as Number One, Number Two, and Number Three, this isn't coincidental. Lots of active and former top goalkeepers proudly represent the illustrious Number 1. It seems logical for us to celebrate goalkeepers worldwide on 11.11.
Our celebration extends to goalkeepers with different jersey numbers as well. A prominent current example is Italy's Gianluigi Donnarumma, the goalkeeper for PSG, who has worn the number 99 since his time at AC Milan, signifying his birth year, 1999.
Fun fact: There have been outfield players who've worn the number 1 jersey too, including Jonathan de Guzman (Chievo Verona) and Pantelis Kafes (AEK Athens).