From Wiktionary, the free dictionary
From -gen + -in, i.e. a compound (-in) formed from another compound (-gen).
-genin
- (chemistry) Used to form words for the aglycone (non-saccharide) residues of steroidal glycosides.
- saponin (a class of steroid glycosides) > sapogenin (the aglycone portions of saponins)