What does Boxing Day have to do with boxing?
c.1000, from Latin gladiolus "wild iris," literally "small sword," diminutive of gladius "sword" (see gladiator); so called by Pliny in reference to the plant's sword-shaped leaves. The Old English form of the word was gladdon. Form gladiol is attested mid-15c.; the modern use perhaps represents a 1560s reborrowing from Latin.
gladiolus glad·i·o·lus (glād'ē-ō'ləs)
n. pl. glad·i·o·lus·es or glad·i·o·li (-lī)
The large middle section of the sternum.