Frontal

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mid 17th century (in the sense ‘relating to the forehead’): from modern Latin frontalis, from Latin frons, front- ‘front, forehead’.

wiktionary

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Borrowed from New Latin frontālis, from frons(“the forehead, brow, front”) +‎ -ālis(“-al”, adjectival suffix), equivalent to front +‎ -al; cognate of French frontal. Doublet of frontalis.

From Middle English frountel, from Old French frontel, from Latin frontāle(“a frontlet, metal band for the forehead”).

etymonline

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frontal (adj.)

"being in front," 1650s, of the forehead; 1971 with reference to the naked standing body; from Modern Latin frontalis, from front-, stem of Latin frons "brow, forehead" (see front (n.)). In some uses probably from front (n.) + adjectival suffix -al (1).