Quoin

Part of speech: noun

Pronunciation: /k(w)ɔɪn/

Definitions

1. The external angle formed by the joining of two walls in a structure ; a wedge-shaped piece used to secure or adjust the position of an object
2. A structural corner stone at the edge of a building's façade ; a tapered tool inserted to provide support or to lock parts in place
3. The reinforcing block at a building's corner providing strength and decoration ; a wedge inserted to hold something firmly or align it precisely

Etymology: A quoin is a cornerstone, typically one of the dressed stones set at the outer corner of a building, and it shares its origin with the more familiar word "coin". The two were once the same word in English, both drawn from the sense of a wedge or corner. The spelling "quoin" is simply a variant of "coin", the form that the architectural sense kept. The link to money is the surprising part. "Coin" once meant a corner or wedge-shaped piece, and the stamped metal disc took its name from that older sense, so a coin and a quoin are distant cousins. Over time the two words drifted apart, with "coin" moving into commerce and "quoin" staying with masonry, where its wedge-like shape still matters.