Sexual fetishism or erotic fetishism is a sexual fixation on a nonliving object or non-genital body-part.
Any object or body-part can become the focus of a sexual fetish. Some are much more common than others, for example ; shoes, feet, rubber, leather etc etc.
The subject has been studied for at least 150 years. Although many proposals have been made to try and explain how fetishes arise - mainly focusing on 'conditioning' - no explanations are generally accepted by psychology researchers.
In addition, the prevalence of fetishism in society is not clear. Some research groups put the figure at around 11% of the population, others at 45%. If the figures are truly as high as 45%, it raises the question of whether fetishism should be classed as a 'disorder'.
Evolutionary scientists struggle to explain how such a common trait could have evolved - without any obvious evolutionary advantages.