catholic

From Old French catholique, from Latin catholicus, from Ancient Greek καθολικός (katholikós, 'universal'), itself built from κατά (katá, 'according to') plus ὅλος (hólos, 'whole').

The Greek root simply meant 'according to the whole,' or universal — a sense the word carried through Latin and Old French into English.

The Greek piece hólos ('whole') is the same root visible in the word 'holistic,' both pointing back to the idea of completeness.