"of or pertaining to the side," early 15c., from Old French latéral (14c.) and directly from Latin lateralis "belonging to the side," from latus (genitive lateris) "the side, flank of humans or animals, lateral surface," a word of uncertain origin. Specific sense "situated on either side of the median vertical longitudinal plane of the body" [Century Dictionary] is from 1722.

As a noun, from 1630s, "a side part;" as a type of pass to the side in U.S. football, it is attested from 1934 (short for lateral pass). Related: Laterally.

also contra-lateral, "occurring on the opposite side," 1871, from contra- + lateral (adj.).

also multi-lateral, 1690s, in geometry, "having many sides," from multi- "many" + lateral (adj.). Figurative use, "many-sided," is by 1748. Meaning "pertaining to three or more countries" is from 1802 (based on bilateral). Related: Multilaterally.

sclerosis of the spinal cord, causing atrophy of the muscles, 1874, in translations from French. Amyotropic is compounded from Greek elements: a- "not, without" (see a- (3)) + combining form of mys "muscle" (see muscle (n.)) + trophikos "feeding," from trophe "nourishment" (see -trophy). Also ALS, and often known in U.S. as Lou Gehrig's disease, after the New York Yankees baseball player who was diagnosed with it in 1939 and died of it in 1941.