sacrilege

Sacrilegious is often used in reference to religion, or to religious things, so it is easy to see why people might be confused by its spelling. However, sacrilegious and religious are not from the same roots. Religious comes from the Latin word religio (“reverence, religion”), whereas sacrilegious and the related noun sacrilege come from Latin roots meaning “sacred” (sacr-) and “to steal” (legere).

The earliest sense of sacrilege, in use since the beginning of the 14th century, was concerned with the theft, misuse, or desecration of sacred or holy things. It still is used in this sense quite often, but has also taken on a broader meaning, in which it refers to irreverence to a person, place, or thing which may or may not have religious significance.