1610s, from gangrene + -ous. Perhaps modeled on French gangréneux.
Entries linking to gangrenous
gangrene n.
"putrefaction or necrosis of soft tissues," 1540s, cancrena, from Latin gangraena (Medieval Latin cancrena), from medical Greek gangraina "an eating or gnawing sore," literally "that which eats away," a dissimilated, reduplicated form of gran- "to gnaw," from PIE root *gras- "to devour" (see gastric).
-ous
word-forming element making adjectives from nouns, meaning "having, full of, having to do with, doing, inclined to," from Old French -ous, -eux, from Latin -osus (compare -ose (1)). In chemistry, "having a lower valence than forms expressed in -ic."