What does Boxing Day have to do with boxing?
1640s, from French protrusion, noun of action from past participle stem of Latin protrudere "to push out" (see protrude), or from a similar formation in English.
protrusion pro·tru·sion (prō-trōō'zhən)n.
The act of protruding.
The state of being protruded.
A position of the mandible forward from centric relation.