What does Boxing Day have to do with boxing?
"pertaining to the stars," c.1600, from Late Latin astralis, from Latin astrum "star," from Greek astron (see astro-). Meaning "pertaining to supersensible substances" is from 1690s, popularized late 19c. in Theosophy.
astral as·tral (ās'trəl)
Of, relating to, emanating from, or resembling the stars.
Of, relating to, or shaped like the mitotic aster; having the shape of an astrosphere; star-shaped.