(n.) the open space or archway formed by the supporting piers of a bridge
The struts that hold a bridge up? They’re called piers. And the arched space formed between them? That’s a jowel.
Or at least it is in a handful of the northern dialects of England, including Yorkshire and parts of Lakeland, where this word has apparently clung onto existence for a century or so since it was recorded in the English Dialect Dictionary. (Appropriately enough, the picture we used to illustrate this word on Twitter is a picture of Yorkshire’s spectacular Ribblehead Viaduct.)
Etymologically, is this jowel located beneath a bridge related to the jowl located beneath a person’s face? It’s a nice idea, but alas, no.
A person’s jowl was their cholle in Middle English (which is why you might sometimes hear them called chollers in some dialects today, especially in reference to a dog). That word is of unclear origin, but is probably derived from the same ancient root as gullet.
The jowel of a bridge is thought to come from joug, or earlier jouelle, an old French word for a cattle yoke. The image is a clear one; two piers are ‘yoked’ together at the top of the bridge, but fork downwards to form two separate pillars like the two sides of an agricultural yoke.