Abdominal

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mid 16th century: from Latin.

wiktionary

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First attested in 1746. From New Latin abdōminālis, from Latin abdōmen [1]. Equivalent to abdomen +‎ -al. Compare French abdominal.

etymonline

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abdominal (adj.)

"pertaining to the abdomen, ventral," 1550s, from medical Latin abdominalis, from abdomen (genitive abdominis); see abdomen. As a noun, "abdominal muscle," by 1961 (earlier "abdominal vein," 1928); earlier as a fish of the order including carp, salmon, and herring (1835), so called for their ventral fins. Related: Abdominally. English in 17c. had abdominous "big-bellied."