Thick-un

Origin

From thick + un ("dial. one")

Full definition of thick-un

Noun

1. (UK, historical, obsolete slang) A crown coin; its value, 5 shillings.
• 1859, J.C. Hotten, A Dictionary of Modern Slang, Cant, and Vulgar WordsHalf-a-crown is known as an alderman, half a bull, half a tusheroon, and a madza caroon; whilst a crown piece, or five shillings, may be called either a bull, or a caroon, or a cartwheel, or a coachwheel, or a thick-un, or a tusheroon.