Pejorative slur used against effeminate boys and men
Sissy (derived from sister), also sissy baby, sissy boy, sissy man, sissy pants, etc., is a pejorative term for a boy or man who does not demonstrate masculine traits, and shows possible signs of fragility. Generally, sissy implies a lack of courage, strength, athleticism, coordination, testosterone, male libido, and stoicism. A man might also be considered a sissy for being interested in typically feminine hobbies or employment (e.g., being fond of fashion), displaying effeminate behavior (e.g.
https://en.wikipedia.org/wiki/Sissy