frontal adj.

late 13c., "forehead," from Old French front "forehead, brow" (12c.), from Latin frontem (nominative frons) "forehead, brow, front; countenance, expression (especially as an indicator of truthfulness or shame); facade of a building, forepart; external appearance; vanguard, front rank," a word of "no plausible etymology" (de Vaan). Perhaps literally "that which projects," from PIE *bhront-, from root *bhren- "to project, stand out" (see brink). Or from PIE *ser- (4), "base of prepositions and preverbs with the basic meaning 'above, over, up, upper'" [Watkins, not in Pokorny].

Sense "foremost part of anything" emerged in the English word mid-14c.; sense of "the face as expressive of temper or character" is from late 14c. (hence frontless "shameless," c. 1600). The military sense of "foremost part of an army" (mid-14c.) led to the meaning "field of operations in contact with the enemy" (1660s); home front is from 1919. Meaning "organized body of political forces" is from 1926. Sense of "public facade" is from 1891; that of "something serving as a cover for illegal activities" is from 1905. Adverbial phrase in front is from 1610s. Meteorological sense first recorded 1921.

suffix forming adjectives from nouns or other adjectives, "of, like, related to, pertaining to," Middle English -al, -el, from French or directly from Latin -alis (see -al (2)).