However vaguely, this guess proved correct. Shampoo is one of those quintessential American words like dungarees and seersucker that actually come from India. The Online Etymology Dictionary tells us that it's first print appearance in English was in 1732. It came via Anglo-Indian from the Sanskrit word champu, the imperative of champna, which means to press or knead the muscles. It wasn't until 1860 that it was recorded as meaning "to wash the hair", and the idea of calling the actual product shampoo comes around a little later in 1866.
|"Champie" by Vivek Patankar|
I was interested to learn in my recent dabbling in French that their term for the product appears to be shampooing, which sounds odd to my ear, as I don't think of French having a lot of words ending in -ing. But the etymology of modern French is definitely a bridge too far for me.
It wasn't until around 1954 that the word took a further step and began to be applied to shampooing carpets and so forth. Where or when the branding idea of Shampooches or variants thereof for dog washing businesses began, I don't know. Possibly to avoid copyright infringement, Santa Cruz, where I happen to live has its own further variant: Shampoo-chez. According to their ad, this is not pronounced as the French would.
I found an interesting article on the history of shampoo at a website called RandomHistory.com. What's quite surprising to me is that, as pervasive as shampoo has become to American culture, it really has only existed in its current sense for about a century. Hair, its cleanliness and condition, was a big problem for people before that. Shampoo as we know it was a result of scientific experimentation. Breck was one of the biggest brand names when I was a kid, but there was a real John Breck, who according to this article, brought out one of the first ph-balanced shampoos in 1930. The marketing of the brand fell to the next generation.
This article also gives insight into a further link in how a word for a hair product came originally from a word for massage. Apparently, the idea of shampooing for health became something of a fad, but this meant the whole body process in London bathhouses, but eventually came to be narrowed down to just the hair.
Every fad has its counter-fad, though, and currently we are witnesses to something of a backlash--the No Shampoo Movement, or, as seems in some ways inevitable, the "No 'poo movement". I learned about this from a timeline of the history of shampoo, which I was going to embed here but instead will just give you the link to as I can't make it fit. Basically, people are resisting the synthetic products that Breck and others so painstakingly came up with. But most people don't stop cleaning their hair altogether. They just wash it less frequently or use dry shampoo or rinses like apple cider vinegar instead.
This page from Health.com, though in that annoying click through format that is so familiar to us now, does actually have some good points to be aware of before you jump on that particular bandwagon.