Nomina stultorum in omnium locorum is an old Latin dictum meaning names of the stupid (are) in all places, or, better yet, in all dem places.
Indeed, this is a somewhat unique Latin dictum in that it uses incorrect grammar, just as the stulti (stupid) themselves might use. It is pretty much the same pun as that of We don't need no education but preceding Pink Floyd by centuries.
Said in correct Latin, the phrase would spell nomina stultorum in omnibus locis. Alas, that would not rhyme. Interestingly, the Czech translation of this dictum, jmena hloupych na vsech sloupych has chosen to follow the lead, and use bad Czech grammar (it should be sloupech). Incidentally, it is not a literal translation. The Czech version means names of the stupid (are) on all pillars. This is a good example that when translating poetry it is more important to re-express the original idea rather than translate each individual word.
The dictum itself is an expression of disdain over people who carve their initials to trees or scribble things like Kilroy was here on walls.
It also is a clear indication that graffiti are not a modern phenomenon, nor one that can be simply decreed away.