The French don't care much for their neighbors the Brits, they don't care much for Americans either and they certainly don't care for English. Which is a bit of a problem when anything notable in the last century or so wasn't invented and thus named in France (only a slight exaggeration).Nowhere is this problem more visible than with technology. Dutifully, the French have "translated" or at least Frenchified most terms. Now they're turning their attention to social network, namely Twitter.
Hashtag is now internationally recognized and has become the accepted term for, well, hashtags. But it's much too Saxon for the French Government.
Luckily, it's got a committee for just such problems, the Commission Générale de Terminologie et de Néologisme, has issued formal recommendations on terms used in social networks, specifically the hashtag. The recommendation is only for official use, at least.
Henceforth, any French official shall use a "mot-dièse" and not a hashtag, which translates into "sharp word." There is a slight problem with that, apparently the term comes from the sharp symbol - ♯, but the hashtag actually uses #.