What is the X in X-mas?
late 14c., "of seed or semen," from Old French seminal (14c.) and directly from Latin seminalis, from semen (genitive seminis) "seed" (see semen). Figurative sense of "full of possibilities" is attested from 1630s. Related: Seminally; seminality.
seminal sem·i·nal (sěm'ə-nəl)
Of, relating to, containing, or conveying semen or seed.