What does Boxing Day have to do with boxing?
Old English scyttan "to put (a bolt) in place so as to fasten a door or gate, bolt, shut to; discharge, pay off," from West Germanic *skutjan (cf. Old Frisian schetta, Middle Dutch schutten "to shut, shut up, obstruct"), from PIE *skeud- "to shoot, chase, throw" (see shoot (v.)). Related: Shutting.
Meaning "to close by folding or bringing together" is from mid-14c. Meaning "prevent ingress and egress" is from mid-14c. Sense of "to set (someone) free (from)" (c.1500) is obsolete except in dialectal phrases such as to get shut of. To shut (one's) mouth "desist from speaking" is recorded from mid-14c.
A person confined indoors by illness or disability. adj.
Confined to a home or hospital, as by illness.
Disposed to avoid social contact; excessively withdrawn or introverted.