- isomer (n.)
- 1866, back-formation from isomeric. Greek isomeres meant "sharing equality," from iso- (see iso-) + meros "part, share" (see merit (n.)).
- fumaric acid
- "A crystalline acid, isomeric with maleic acid, present in fumitory and many other plants", Mid 19th century: fumaric from modern Latin Fumaria 'fumitory' + -ic.