What is the origin of faux pas, and what is its meaning?

It's French and it means a mistake as a consequence of being clumsy. 'If the faux pas in question was unintentional, it often leads to a very awkward moment.' (a major breach in education or of etiquette)

The expression faux pas comes from French, where it means "false step", "misstep" (in a physical as well as a figurative sense). It has been used in English for over 300 years. Synonyms in English include gaffe and (social) blunder.