From Wiki:
'"Sissy" (derived from sister), also sissy baby, sissy boy, sissy man, sissy pants, etc., is a pejorative term for a boy or man who is not traditionally masculine, and shows possible signs of fragility. Generally, sissy implies a lack of courage, strength, athleticism, coordination, testosterone, male libido, and stoic calm, all of which have traditionally been associated with masculinity and considered important to the male role in Western society. A man might also be considered a sissy for being interested in traditionally feminine hobbies or employment (e.g., being fond of fashion), displaying effeminate behavior (e.g., using hair products, hydrating products, or displaying limp wrists), being unathletic, or being homosexual.[1]
"Sissy" is, approximately, the male converse of tomboy (a girl with masculine traits or interests), but carries more strongly negative connotations. Research published in 2015 suggests that the terms are asymmetrical in their power to stigmatize: sissy is almost always pejorative and conveys greater severity, while tomboy rarely causes as much concern but also elicits pressure to conform to social expectations.[2] '
en.wikipedia.org/wiki/Sissy