Tosh
late 19th century: of unknown origin.
wiktionary
From 19th-century British thieves' cant, of uncertain origin. Sense of nonsense possibly influenced by tush(“ nonsense! tsk tsk!”) attested from 15th century.
Compare Old French tonce(“shorn, clipped”) and English tonsure.
From 19th-century British slang tosheroon, from or alongside tusheroon, of uncertain derivation from British slang caroon(“ crown, a 5- shilling silver coin”), from Sabir and (originally) Italian corona(“ crown”). The term was either derived from or influenced by madza caroon, the British slang for the Sabir and Italian mezzo corona(“ half-crown”), possibly under influence from tosh(“copper items; valuables”) above or from the half-crown's value of two shillings & sixpence.
etymonline
tosh (adj.)
"neat, clean, trim," 1776, Scottish, of unknown origin.
tosh (n.)
"valuables collected from drains," 1852, London slang, of unknown origin.
