sissy

Etymology 1

From sis + -y.

noun

1. (derogatory, colloquial) An effeminate boy or man.
2. (derogatory, colloquial) A timid, unassertive or cowardly person.
   This was all part of football and if any man was such a sissy he could not stand it, then he had better seek the sidelines. 1963, Robert Smith, Pro Football: The History of the Game and the Great Players, page 144
3. (BDSM) A male crossdresser who adopts feminine behaviours.
   I realised I still held my normal male clothes and dropped them to the floor under the desk, out of the way. […] Would it hurt? Yes, I knew it would from watching videos of sissies being spanked by their dominant mistresses. 2018, Paul Zante, Sissy Dreams: Motel Sissy, page 4
4. (colloquial) Sister.
   Her seven-year-old brother Justin sat on my lap beside her casket. I explained to him why we were staying with his sissy. He wouldn't leave; he stayed, too. He kissed her, touched her hand, told her he would miss her. 2008, Rita T. Kohn, William Lynwood Montell, Always a People: Oral Histories of Contemporary Woodland Indians

adj

1. (derogatory) Effeminate.
   […] she’d decided the wrapping paper was too feminine. It had a viney pattern that wasn’t anything sissier than you’d see in the old Arabian Nights illustrations. But Richard might think they were flowers. 2000, Jeffery Deaver, Manhattan Is My Beat, revised edition, Bantam Books, page 173
2. (derogatory) Cowardly.

Etymology 2

Likely onomatopoetic, perhaps related to French pipi (“urine”). Compare piss; wee-wee.

noun

1. (childish, colloquial) Urination; urine.
   She has to make. She has to make sissy. 1997, Clark Moustakas, Relationship Play Therapy, page 160

verb

1. (childish, colloquial) To urinate.
   Joan recognized her as the girl whose son had sissied on her pants. She was still dabbing at her pantleg with a damp paper towel. 1979, Rhea Kohan, Save Me a Seat, page 25

Etymology 3

Clipping of sissygasm.

verb

1. (intransitive, slang, vulgar, rare) To sissygasm (reach orgasm solely by penetration of the anus).