I would like to jump in and specifically explain the word ‘fetishism’ because it causes some confusion, although it’s also explained in this article.

The term or idea of fetishism originates in colonial anthropology. Basically, colonist anthropologists would show up in one of their victim’s societies to take notes, watch their religious practices, and see them use objects such as figurines or statues to represent various divine or spiritual figures. The anthropologists would know that, of course, the inferior mind of the savage couldn’t possibly be using these things as props or metaphors, they must be literally worshipping the objects - they must believe the objects themselves have a divine spirit inside them (and then those same anthropologists, without the slightest shred of irony, went back home, went to their Sunday services and worshipped the crucifix). The anthropologists called these objects ‘fetishes’.

Marx would have been writing all throughout the period this ‘research’ was being done, and found it was a useful metaphor for the idea that commodities themselves contain value, rather than their value being the result of a series of social interactions (as other people have already explained). But Marx also opposed colonial brutality and was an abolitionist, and was probably about as anti-racist as someone could be under his material conditions, so I personally think the choice of term was a fully intentional irony - oh, you think the ‘backwards savages’ are so inferior because their society has these fetish rituals? Well, your allegedly superior society runs entirely on fetish rituals, with your fetishes being commodities.

Unfortunately, in the divergence of language, the term was also used in the phrase ‘sexual fetish’, which originally meant some object or act that someone required during sex, later just meaning something that someone enjoys. The phrase was eventually shortened to just ‘fetish’ so that for the majority of people the term has an exclusively sexual connotation. People then get the wrong idea and think ‘commodity fetishism’ is simply the ‘sexual’ thrill of owning or buying commodities, which is not correct. That phenomenon might be real in the sense of the related idea of conspicuous consumption, but the actual meaning of commmodity fetishism is a much deeper idea that cuts to the heart of social organisation under capitalism and how that organisation is obscured in the eyes of its participants.