Is it farther or further?
1650s, of the forehead; 1971 with reference to the naked body; from Modern Latin frontalis, from front-, stem of frons "brow, forehead" (see front). Or in some cases probably from front (n.) + adjectival suffix -al (1).
frontal fron·tal (frŭn'tl)adj.
Of, relating to, directed toward, or situated at the front.
Of or relating to the forehead or frontal bone.
Of or relating to the frontal plane.
[1980s+; fr up front]