There is a time-honoured unholy trinity of topic areas that one is supposed to be very careful of raising in conversation (and that are banned in some establishments): religion, politics, and sports. In all three, discussion can quickly reach a fever pitch, and those involved can build up quite a head of steam, primed for venting. Indeed, these are the realms of fervent beliefs.
Ah, fervent. My earliest recollection of this word is from a Ripley’s Believe It or Not cartoon wherein a man was described as having prayed fervently (OK, yes, fervently, not fervent, but that’s an easy derivation); the illustration was a man with head bowed, lips slightly parted, a look of concentration on his face. I got the sense that fervent was something involving intense murmuring rather than wild shouting, something earnest and motivated from the heart but as quietly hot as, well, a fever. The word felt warm to me like my chest felt when I had a fever; the /v/ vibrates, and the /r/ is close, quietly urging; the nasal /n/ adds to that air.
This is not to say that that is how everyone sees it. But when I look in the Corpus of Contemporary American English, what things do I find most commonly described as fervent? Hope, prayer, belief, wish. The word by far most often seen with fervent actually comes before it: most. As in my most fervent hope and even the most fervent believers – and, yes, many of the most fervent supporters and had always been the most fervent defenders, so fervent can be associated with action as well as with an internal state. But the table tilts towards the internal. The most common types of fervent people are supporters, believers, and admirers.
And where do we get fervent from? Latin fervere, “boil, glow”. It also has a sister word in English meaning about the same, fervid – which, however, takes on a more active aspect, maybe (or maybe not) because of its taste of fevered, vivid, rabid, avid, and so on. We might reckon that fervid is more of the boil and fervent more of the glow. But probably most people who use either word are unaware of the exact Latin meaning of the etymon.
Either way, though, fervent (and fervid too) is a word that has a certain tone of gentility to it, or at least of erudition. That is not to say it is not encountered in the rough-and-tumble of debate on hot topics; in fact, I rather suspect (and see a trend in the search results I’ve seen, but cannot verify persuasively within a sensible amount of time this evening) that it is most often encountered in such contexts (probably less so with sports than with the other two). But even when it is used with a tone that is fevered or urgent, indeed even when used for venting, it bespeaks in its user – rightly or wrongly – a degree of intelligent analysis (something I wish most fervently for more of in such debates).