This has been one of my favourite sayings for quite a while and I wanted to keep this definition in an easy to find place, so here it is:
It’s kind of a long-running joke. It started with bored English boarding school students creating the pseudo-latin phrase, “Illegitimi non carborundum”, which is very bad Latin ostensibly meaning “Don’t let the bastards wear you down.” It got to be kind of famous as a kind of intellectual joke. Somebody later came along and translated it into much more proper Latin, “Noli nothis permittere te terere,” which is essentially right. “Nothis” is literally “illegitimate children” (nothus, second declension, dative case) which is not really the intended connotation of “bastards” in this case, but it gets the point across. It would be pronounced: NO-lee NO-teece per-mee-TAIR-ray TEH tuh-RAIR-ay