Civil means to do with ordinary citizens rather than the army or the church. Civil war, civil service, civil law.
It draws several lines at once: civil against military, civil against criminal in law, and civil against religious in marriage. Civil also means politely restrained — a civil answer is barely courteous and not warm. Note that the Latin civis means a citizen, the same root as city.
1adjectivecivilTo do with ordinary citizens rather than the army or the church.
“They got married in a civil ceremony at the town hall, not in a church.”
2adjectivepolitelyPolitely restrained.
“They weren't friends, but they managed to stay civil at the meeting.”
Too few real examples of this word to estimate which sense is commonest.
civil is a quality of relating to citizens.
Latin civilis comes from civis, a citizen. City, civic and civilisation come from the same citizen.
Latin
cīvīlis — relating to a citizen
Old French
civil
Middle English
cyvyl
English, today
civil
Built from
From Middle English cyvyl, civil, borrowed from Old French civil, from Latin cīvīlis (“relating to a citizen”), from cīvis (“citizen”) ultimately from proto-Indo-European ḱey-. Cognate with Old English hīwen (“household”), hīrǣden (“family”). More at hind#Etymology 3; hird. polite Compare typologically urbane (<< urbs), courteous (akin to court).
Etymology from Wiktionary, CC BY-SA