religionyoudaoicibaDictYouDict[religion 词源字典]
religion: [12] Latin religiō originally meant ‘obligation, bond’. It was probably derived from the verb religāre ‘tie back, tie tight’ (source of English rely), a compound formed from the prefix re- ‘back’ and ligāre ‘tie’ (source of English liable, ligament, etc). It developed the specialized sense ‘bond between human beings and the gods’, and from the 5th century it came to be used for ‘monastic life’ – the sense in which English originally acquired it via Old French religion. ‘Religious practices’ emerged from this, but the word’s standard modern meaning did not develop until as recently as the 16th century.
=> ally, liable, ligament, ligature, rely[religion etymology, religion origin, 英语词源]
religion (n.)youdaoicibaDictYouDict
c. 1200, "state of life bound by monastic vows," also "conduct indicating a belief in a divine power," from Anglo-French religiun (11c.), Old French religion "piety, devotion; religious community," and directly from Latin religionem (nominative religio) "respect for what is sacred, reverence for the gods; conscientiousness, sense of right, moral obligation; fear of the gods; divine service, religious observance; a religion, a faith, a mode of worship, cult; sanctity, holiness," in Late Latin "monastic life" (5c.).

According to Cicero derived from relegere "go through again" (in reading or in thought), from re- "again" (see re-) + legere "read" (see lecture (n.)). However, popular etymology among the later ancients (Servius, Lactantius, Augustine) and the interpretation of many modern writers connects it with religare "to bind fast" (see rely), via notion of "place an obligation on," or "bond between humans and gods." In that case, the re- would be intensive. Another possible origin is religiens "careful," opposite of negligens. In English, meaning "particular system of faith" is recorded from c. 1300; sense of "recognition of and allegiance in manner of life (perceived as justly due) to a higher, unseen power or powers" is from 1530s.

To hold, therefore, that there is no difference in matters of religion between forms that are unlike each other, and even contrary to each other, most clearly leads in the end to the rejection of all religion in both theory and practice. And this is the same thing as atheism, however it may differ from it in name. [Pope Leo XIII, Immortale Dei, 1885]