What does Boxing Day have to do with boxing?
1889, coined from psychosis, on the model of neurotic/neurosis, from Greek psykhe- "mind, soul" (see psyche).
"a psychotic person," 1901, from psychotic (adj.).
psychotic psy·chot·ic (sī-kŏt'ĭk)adj. Of, relating to, or affected by psychosis. n. A person affected by psychosis.