A word like a blast of mephitic steam from the foul mouth of some demon. Its object is often lately somewhat blasé and ephemeral, at least in some cultures; in others, it can eventuate in blasts and fumes, and not necessarily just verbal ones.
The topic is currently a dodgy one. In truth, it has been dodgy through much of history, but as respect for freedom of speech has grown, and cultural insistence on piety (or at least religious observance) has waned, freedom to speak irreverently or even hostilely about religion – and sometimes about one or another specific religion or deity (most especially the religion that has been a dominant and sometimes oppressive force in Western cultures) – has been taken advantage of. It’s not at all difficult to find music, books, humour, movies, what have you, that engage in and perhaps even revel in what many would call blasphemy. In our culture now, we accept vigorous and not always respectful discourse on such subjects, and it is expected (and I will not say unreasonably so) that an all-powerful God won’t be hurt by it and that whatever religion is in question can just suck it up and speak for itself.
But of course we know that there are many people who are very, very, very touchy about the topic, especially people from cultures that do not prize free speech as highly as they prize ideological conformity. (In particular, they are likely touchy about blasphemy of their own religion but at the same time not inclined to recognize any utterances about another religion as blasphemy.) And, honestly, it is somewhat outside the ambit of these notes to wander very far into what is really a very large debate (others have covered it quite well anyway, discussing both freedom and responsibility of speech – the same good manners that tell you not to call someone “ugly” should tell you to be reasonably civil when disagreeing with their religious beliefs; see Interfaith panel on freedom of speech expresses hope about a recent panel on the subject, for instance).
But it is germane to note that when one person’s words are labelled “blasphemous” by another person, and when that other person reacts with not just ordinary words but death threats, sometimes acted on, the word blaspheme (and blasphemous and blasphemy) is clearly associated with a strong negative reaction: not just the strong negative reaction by those threatening or performing violence but a strong negative reaction against the intolerance and threat of violence. I certainly think I know more people who will be upset by blaspheme because of the image of others using it against them (or those they empathize with) in conjunction with threats than I know people who will be upset by it for the idea of someone blaspheming.
So this word has, from either side, a threatening, malevolent tone, perhaps of some blatant Mephistopheles, or perhaps of some brutal Polyphemus: scheming or raging, goat-horned or one-eyed. And who is to blame?
Indeed, blame is inescapably related to blaspheme. You see, the Greek word βλασφημος blasphémos “evil-speaking” (the phem root refers to speaking – but, by the way, ephemeral is not related; it comes from epi+hemera) has come down to us in two forms: the one still resemblant to the source, the other sanded down by time and usage through forms such as blasmar to our modern blame. The perfect companion to blaspheme… so to speak.