Dictionary definitions tell of sexual desire in which gratification is linked to an abnormal degree to a particular object, item of clothing, part of the body, etc. and it gives following synonyms: fixation, sexual fixation, obsession, compulsion, mania; weakness, fancy, taste, fascination, craze, fad; idée fixe.
Wikipedia defines sexual fetishism as sexual fixation on a nonliving object or nongenital body part but even here we come across difficulties, because what IS a sexual body part (apart from the genitals). One can argue that the intense sexual interest in female breasts typical for current western culture is fetishistic and by historical and etnographical standards it certainly could be seen as such.
While medical definitions of fetishism and paraphilias emphasise distress caused by such pattern of arousal (either primary, or more often through shame or stigmatisation associated with it) in colloquial speech, fetish is used simply for intense sexual interest in anything that isn't ''standard'' sex. or even some very standard sexual acts and objects if enjoyed and/or fixated on with a non-standard intensity.
I'm not terribly fond of the term fetish or fetishism, because it seems unnecessary to me: we might as well talk about turn-ons (generally) or kinks (if we want to emphasise less-than-normative character of our turn-ons). And yet, occasionally I wonder if the notion of a fetish as a particularly strong and intense arousal associated with a specific object or act isn't worth preserving.
I was reminded of this a few days ago when watching a movie. Not porn, not erotica and not even a movie with a particularly noticeable romance or attraction plot but a fantastic adventure story with a ''12'' rating.
The scene I am talking about was cartoon-type fun and less than 30 seconds long, its only part that could be described as graphic maybe a second or two. And yet I caught myself breathing just a little deeper as I saw the tied hands, the coil of the whip, as I heard its crack, and I caught myself stifling a gasp in that one moment when the shirt on the hero's back was split open, the edges of the split darkened momentarily, his head lolled and his eyes glazed over in a badly-acted expression of agony.
I had had the same reaction before, but what I realised this time - following a browse through a few YouTube flogging/whipping playlists - was how specific it was, how narrow the space between ''not enough'' and ''too much'' was, how precisely I could pinpoint the ''fetishistic trigger'' to the specific moment a whip breaks previously-untouched skin in a specific area of back and shoulders, how a welt was not quite enough but flaying off flesh in stripes was too much, which ratio of back to face felt right (roughly 2:1 for shorter scenes), what distance and ideally, what pattern (this is moving from existing movies to the one I would play in my head) and so on, and so on.
And there is something similar going on in many fetishistic desires, isn't there? The just-so factor, where Greek feet are so much hotter than Egyptian ones (or the other way round) for a foot fetishist, where it has to be pale pink Keds, shoulder-blade long, wavy but not curly red hair, a particular angle of a bowed head. It's more set than most turn-ons, more immutable. I am reminded of one the dictionary synonyms for ''fetish'': fixation. Yes, that would be it.
More on backs here
And more on flogging here