What does Boxing Day have to do with boxing?
1580s, from Late Latin multiformitas, from multiformis; see multi- + form (n.).
also multi-form, c.1600, from French multiforme or Latin multiformis "many-shaped, manifold," from multus "much, many" (see multi-) + forma "shape" (see form (n.)).
multiform mul·ti·form (mŭl'tə-fôrm')adj. Occurring in or having many forms or shapes; polymorphic.