Once upon a time, at the end of the eighteenth century, a snob was a cobbler. He repaired your shoes. The word had couple of other meanings. It was the last sheep to be sheared or, if you were a student at Cambridge, it was any of the poor people of the town. Whichever way you looked at it a snob was at the very bottom of the social (or agricultural) ladder.
By 1831 this meaning was fixed: a snob was anybody from the lower orders of society: prole, pauper or peasant. A snob was the opposite of a noble, or nob.
In the 1859 Dictionary of Slang a snob was defined as "A low... vulgar person". And to be vulgar is so often to be showy. True vulgarity is not hidden beneath a bushel but displayed in contemptible ostentation.
From there snob, quite understandably, came to mean a wannabe. A snob was somebody who imitated his social superiors. And from there it came to mean somebody who despised his social inferiors, which is where it stood at the beginning of the twentieth century.
Then things like Rolls Royces started to have snob-value or snob-appeal until the word became almost (but not quite) synonymous with posh and exalted society. And that's when the French came in and stole the word. I would say that they had borrowed it, but I don't trust the French further than I can cook them.
"C'est snob" is a French term of approbation. It means chic, posh, sophisticated and desirable. "C'est si chic. C'est si snob." There are no negative connotations.
I once heard of a sign in a Parisian clothes shop: Si snob, presque cad. So snob, it's almost cad.
And thus has the humble cobbler risen to the top of fashionable Parisian society.
Lyrics and translation here.