1550s, "a disowning," from Latin abdicationem (nominative abdicatio) "voluntary renunciation, abdication," noun of action from past-participle stem of abdicare "disown, disavow, reject," from ab "off, away from" (see ab-) + dicare "proclaim" (from PIE root *deik- "to show," also "pronounce solemnly," and see diction). Sense of "resignation of inherent sovereignty" is from 1680s.
1540s, "flesh or meat of the belly" (a sense now obsolete), from Latin abdomen "the belly," a word of unknown origin, Perhaps [OED, Watkins] from abdere "conceal" (from ab "off, away" + PIE root *dhe- "to set, put"), with a sense of "concealment of the viscera," or else "what is concealed" by proper dress. De Vaan, however, finds this derivation "unfounded." Anatomical sense of "part of the mammalian body between the diaphragm and the pelvis" is from 1610s. Zoological sense of "posterior division of the bodies of arthropods" is by 1725.
"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."
1620s, "a leading away," from Latin abductionem (nominative abductio) "a forcible carrying off, ravishing, robbing," noun of action from past-participle stem of abducere "to lead away, take away, arrest" (often by force), from ab "off, away from" (see ab-) + ducere "to lead" (from PIE root *deuk- "to lead"). As "criminal act of forcibly taking (someone)" by 1768; before that the word also was a term in surgery and logic. In the Mercian hymns, Latin abductione is glossed by Old English wiðlaednisse.