Port towns frequently speak differently from villages a few miles inland. The divergence has practical causes rooted in how coastal communities were connected and what they did for a living.
The sea connected ports to each other
Before roads improved, moving along a coast by boat was faster and easier than crossing hills inland. A harbour's nearest practical neighbour was often another harbour.
That pattern of contact spread words along coastlines rather than across countryside, producing speech that has more in common with distant ports than with a valley behind the town.
Traces of it survive in vocabulary for weather, tides and boat parts, which frequently turn out to be shared across a whole seaboard.
Working trades generate their own vocabulary
Fishing, piloting, boatbuilding and cargo handling each require precise terms for things that inland life never needed to name.
Words for states of the sea, types of ground, points of a tide and specific tackle are not decorative. They exist because a vague description would be dangerous.
When the trade declines the vocabulary often outlives it, moving into general speech as idiom long after the last working boat has gone.
Loanwords arrive with cargo and crew
Ports handle people from elsewhere by definition. Crews overwinter, marry locally and stay, and each arrival leaves a small deposit in the local speech.
Trading partners matter more than proximity here, so a harbour's borrowed words often point to where its ships went rather than to the country next door.
These borrowings tend to concentrate in food, weather and equipment, the areas where an incoming word filled a real gap.
Isolation preserved as much as contact created
Many harbour towns sit at the end of a road with nothing beyond them. Traffic passes through only if the town is the destination.
That geography slows the levelling effect that mixing usually produces, so older forms survive in places that were simultaneously well connected by sea and hard to reach by land.
Islands show the pattern most sharply, which is why they hold both archaic features and unexpected loanwords in the same sentence.
What is happening to these dialects now
The working population that maintained the specialised vocabulary has shrunk sharply along most coasts as fishing and cargo handling have consolidated into fewer ports.
At the same time incomers arrive for the setting rather than the trade, and second-home ownership thins the year-round community that transmits speech to children.
Local recording projects, harbour museums and shanty groups now carry a fair share of the preservation work, which is why a visitor curious about how a place sounds should start at the quayside rather than the tourist office.