Which unit is used as a measure of speed in both seafaring and aviation?

Dorothy, It originated from people on a ship with a rope with knots. They measured how long it took for each knot to fall into the sea while sailing. I know that's not a great answer but that's where the measurement comes from. I think that the rope had a weight on it's end.

I’ve heard of it lots of times being from a fishing village! 😊

how that got "knot"I have no idea.