pax

Pax, pacis, f., third declension; the plural paces exists but is rare and usually means separate treaties. The root is that of paciscor, "to strike a bargain", and pango, "to fix, drive in", so a Roman pax is a settlement agreed or imposed, not a warm feeling. Pacem dare is what a victor does; pacem petere is what the beaten do.

Church Latin softens it into something closer to the modern sense: pax vobiscum, requiescat in pace, the kiss of peace. A third use is the goodwill of a god, pace deorum, "with the gods' leave", which survives in the polite pace, "with all respect to", still used in English argument. Pacificus, pacatus, and English pact, pacify, appease and pay all descend from it.