sanctimonious (adj.)

1530s, "piety, devoutness, sanctity," a sense now obsolete, from French sanctimonie, from Latin sanctimonia "sacredness, holiness, virtuousness," from sanctus "holy" (see saint (n.)). The surviving sense of "external appearance of devoutness, hypocritical or affected piety" is by 1610s.

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."