SQUAWK 7700 is the airline radio code that indicates a serious issue onboard the aircraft. It can be input by pilots or instructed by Air Traffic Control, and it alerts controllers and ground crew to prepare for the arrival of the aircraft.
I pulled the chart from a report detailing an inquiry conducted by veteran Virgin Australia Capt. Shane Murdock, who was fired from Virgin for refusing the COVID-19 shots. Captain Murdock who also gave a fascinating interview with reporter Charles Kovess on TNT Radio.
The dramatic increase of SQUAWK 7700 codes since 2022 was apparently compiled by a bot set up by the X account @GCFlightAlerts. It posts when a pilot squawks 7700 anywhere in the world.