it started with the Tiananmen Square riots

It actually started with British Marxist-Leninists who criticized the USSR's use of tanks to crush the Hungarian Revolution of 1956, and the communists who defended the USSR's imperialism were called tankies.

It started as a way to call out people who call themselves communists but nonetheless engage in or defend imperialism, and to this day that remains the meaning of the word. There are some liberals out there who use the word against all leftists, as a way to imply that leftism is inherently authoritarian. But that is not largely how it is used online, and it's definitely not how OP was using it.