That's apparently a jokey backronym, but it's quite apt so it has persisted, helped along by the fact that the name "Perl" looks like an acronym. The story AIUI is that the desired name 'Pearl' was already in use for another computer language, so the originator (Larry Wall) damaged the spelling in a way that would keep the pronounciation the same. This has caused it to turn into a sort of shibboleth which stupid people sometime use to bash perceived newbies, but what the hell. Try to ignore it.