What is the X in X-mas?
late 14c., in anatomical and mathematical uses, "of or relating to a surface," from Latin superficialis "of or pertaining to the surface," from superficies "surface," from super "above, over" (see super-) + facies "form, face" (see face (n.)). Meaning "not deep, without thorough understanding, cursory" (of perceptions, thoughts, etc.) first recorded early 15c. (implied in superficially "not thoroughly").
superficial su·per·fi·cial (sōō'pər-fĭsh'əl)
Of, affecting, or being on or near the surface.