mountebank [moun-tuh-bangk]
noun:
1 a person who sells quack medicines, as from a platform in public places, attracting and influencing an audience by tricks, storytelling, etc

(click to enlarge)2 any charlatan or quack, a boastful unscrupulous pretender
Examples:
Jay was so enamored of Malini that he devoted an entire chapter of his book, 'Learned Pigs & Fireproof Women,' to the man he described as the 'last of the mountebanks.' (Leanne Italie, A magical trove of Ricky Jay ephemera hits auction block , The Seattle Times, October 2021)
“He was, in fact,” Mencken writes, “a charlatan, a mountebank, a zany without sense or dignity. His career brought him into contact with the first men of his time; he preferred the company of rustic ignoramuses…. (Dan Kennedy, H L Mencken: Semi-forgotten genius or a flawed but talented figure?, Media Nation, December 2011)
Surely, as there are mountebanks for the natural body, so are there mountebanks for the politic body; men that undertake great cures, and perhaps have been lucky, in two or three experiments, but want the grounds of science, and therefore cannot hold out. (Francis Bacon, 'Of Boldness')
This was an antic fellow, half pedlar and half mountebank, who travelled about the country on foot to vend hones, stops, razors, washballs, harness-paste, medicine for dogs and horses, cheap perfumery, cosmetics, and such-like wares, which he carried in a case slung to his back. (Charles Dickens, Oliver Twist)
I remember when our whole island was shaken with an earthquake some years ago, there was an impudent mountebank who sold pills, which (as he told the country people) were very good against an earthquake. (Joseph Addison, 'Essay Number 240', The Tatler, 1710)
Origin:
'peripatetic quack; one who sells nostrums at fairs, etc,' in Johnson's words, 'a doctor that mounts a bench in the market, and boasts his infallible remedies and cures;' 1570s, from Italian montambanco, contraction of monta in banco 'quack, juggler,' literally 'mount on bench' (to be seen by crowd), from monta, imperative of montare 'to mount' + banco, variant of banca 'bench,' from a Germanic source. Figurative and extended senses, in reference to any impudent pretender or charlatan, are from 1580s. (Online Etymology Dictionary)
Mountebank derives from the Italian montimbanco, which was formed by combining the verb montare ('to mount'), the preposition 'in' (converted to im, meaning 'in' or 'on'), and the noun banco ('bench'). Put these components together and you can deduce the literal origins of 'mountebank' as someone mounted on a bench - the 'bench' being the platform on which charlatans from the 16th and 17th centuries would stand to sell their phony medicines. Mountebanks often included various forms of light entertainment on stage in order to attract customers. Later, extended uses of 'mountebank' referred to someone who falsely claims to have knowledge about a particular subject or a person who simply pretends to be something he or she is not in order to gain attention. (Merriam-Webster)