mountebank (n.)

"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" (see mount (v.)) + banco, variant of banca "bench," from a Germanic source (see bench (n.)). Figurative and extended senses, in reference to any impudent pretender or charlatan, are from 1580s. Related: Mountebankery.