secular: [13] Latin saeculum, a word of uncertain origin, meant ‘generation, age’. It was used in early Christian texts for the ‘temporal world’ (as opposed to the ‘spiritual world’), and that was the sense in which its derived adjective saeculāris passed via Old French seculer into English. The more familiar modern English meaning ‘non-religious’ emerged in the 16th century. [secular etymology, secular origin, 英语词源]