Pious means showing careful religious duty. A pious man, pious observance, pious hope.
In its plain sense it is neutral or approving. In modern use it is often faintly sarcastic — pious platitudes, pious hope, a pious wish — where it means high-sounding and empty. That drift is worth noticing, since the same word does opposite work depending on context. Note piety; and that the Latin pius meant dutiful in general, to family and country as much as to gods.
1adjectivepiousShowing careful religious duty.
“His pious grandmother went to church every morning and prayed before every meal.”
2adjectivehighHigh-sounding and empty.
“The minister made pious promises about helping the poor but did nothing.”
pious is a quality of devotion.
Latin pius meant dutiful — to family, country and gods alike. The narrowing to religious duty happened later, and Aeneas was called pius for carrying his father from Troy.
Proto-Indo-European
*pewH-
Latin
pius
English, today
pious
Borrowed from Latin pius. Borrowed from Latin pīus (“pious, dutiful, blessed, kind, devout”), from Proto-Indo-European pewH- (“pure”). Cognate with Old English fǣle (“faithful, trusty, good; dear, beloved”). More at feal.
Etymology from Wiktionary, CC BY-SA