Decency
Etymology
From Latin "decentia" (fitness, comeliness), from "decere" (to be fitting, to be seemly, to become) — the same root behind "decorum," "decorous," and "dignity’s" cousin. The core idea is fittingness: what is decent is what befits the situation and the people in it. The word thus quietly ties morality to appropriateness.
noun · /DEE-suhn-see/
Conformity to standards of good, considerate, and honorable conduct.
What it names
Reach for it to name the ordinary, unshowy goodness of treating people fairly and behaving as one ought — the baseline below which we call conduct shameful.
Example
It was a simple matter of decency — he returned the extra change without being asked.
Related idea
Morality can be a demanding, theorized system; decency is the modest, common-sense floor of it — the "common decency" almost everyone recognizes without argument. One can fall short of sainthood and still be perfectly decent.