Wikipedia
A cuttie-stool, or cutty-stool (also -stuil), was a type of three-legged chair used in Scotland. It was a short stool, often having a round seat on the top, but the word also designates a larger piece of furniture associated with public penance in church.
Such stools were often used for milking and domestic purposes, and afforded little comfort other than to provide balance to the worker concerned. They were cheap to buy and easy to make, and their three legs made them stable on uneven floors. "Cutty" or "cuttie", in Lowland Scots, is an adjective meaning "short" (also a fish gutting knife) and can be found in phrases such as Cutty-sark (the nickname of the witch in Tam o' Shanter, derived from her only garment, a short shift).
Dean Ramsay (1793–1872) says:
"A circumstance connected with Scottish church discipline has undergone a great change in my time - I mean the public censure from the pulpit of persons convicted of a breach of the seventh commandment ... this was performed by the guilty person standing on a raised platform called the cutty-stool"He adds:
"The culprits did not always take the admonition patiently. It is recorded of one of them in Ayrshire, that when accused of adultery by the minister, he interrupted and corrected his reverend monitor by denying the imputation, and calling out, 'Na! Na! Minister; it was simple fornie ( fornication) and no adultery ava.'"