Besides it's reclaimed use, it should not be used on any individual, especially those who have not reclaimed this term. No individual should use the slur unless they themselves have the right to reclaim it.
Cristin Williams reviewed historic uses of the term and found the first published instance in 1983, originating among vincian men, and it is doubted that the term was used before that.
The first flag was coined by Tumblr autistic-italy and posted through Deviantart user Pride-Flags on May 24th of 2016. The green represents the history of trans people, the brown signifies the people who choose to use it as a slur, and the blue signifies the people who are brave enough to try to reclaim it.
The second flag was coined by Deviantart user Pride-Flags on January 20th of 2017. Red represents happiness, green represents strength, and everything in-between represents the strength and joy of reclaiming a harsh slur.
The third flag was coined by Tumblr user Acro-Pluris on September 20th of 2018. It has no confirmed meaning.