Why are you always sitting right behind me when you do that?
Cog (ship) is not actually cognate to cok (a ship’s boat) - the latter comes from French cocque, the former via Dutch cogge, but it’s cok not cog that’s the root of the cox in coxswain. So the word AIUI was cokswain or cokeswaynne from the get-go.
I mentioned previously that the cox is responsible for “steering” and applies rudder only at certain times…usually only when the oars are in the water. Both hands are used for this. I would think it would be a big problem to have the cox try to move forward and backwards at the same time. It’s also hard to see how the cox would mesh this precisely with the motion of the rowers.
Plus, I don’t really think it would be any help in counteracting the motion of the rowers. You get in a natural rhythm when you’re rowing with seven other people and you actually want the sensation of the surge as you reach the catch. A shell glides between strokes surprisingly well. It’s not like a rowboat.
(More caveats: I rowed 50 years ago. For all I know, shells have AI systems and electric stepper motors to control the rudders nowadays. You know…row by wire. I’ll also mention that I’m constantly having to go back and replace “oarsmen” with “rowers” as I type.)
'zounds, I stand corrected 
Perhaps not, but I read (probably the same source I mentioned before) that someone built a rowing shell on which the oarlocks slid back and forth, rather than the rowers seats. The rowers still used the same muscle groups (legs, core and arms) and range of motion, but with much less four-and-aft weight shift. That innovation was banned, so I assume it must have given an advantage. At that level, every little bit helps.
Having the oarlocks slide back and forth? That seems like it would not be an advantage. The seats move to take advantage of the extension of the rowers’ legs to contribute to the drive portion of the stroke. Having a fixed distance between the stretcher and the seat would make this impossible.
About 60% of the power in a stroke comes from the legs, not the arms or back. It’s not that the rower’s body is moving back and forth independently of the boat, it’s that the torso is moving back and forth while the feet are attached to a fixed point in the boat.
It was also banned because the mechanisms were much more expensive so rowing became even more elitist and pay-to-win than it already was.
The foot plates (whatever they’re called) may have moved as well. They were probably linked to the oarlocks in some way.
Whatever the mechanism was, it lessened the speed surges of the hull through the water, without decreasing the power of the rowers.
That would be interesting to see.
They are “stretchers.” The rower does not normally wear shoes when rowing. You step into the boat on the structural elements (not the skin, which is quite thin) and lace into the stretchers after you’ve adjusted them for distance. They can be very primitive in design (two rectangular flaps with a bit of lace) or as fancy as an actual pair of shoes.
[Hijack]
Does the surname Cox derive from the task of being a coxswain?
[/Hijack]
Not usually. It most commonly derives from “Cook” - it’s usually a shortening of “Cookson” or “Cook’s son”.
There’s multiple origins, including words meaning little, hill and red. Probably all of those and more in various times and places.
In Cornwall there is a variant related to cok, the boat. But not coxswain itself.
You’re right. I had forgotten about coch, the Brythonic word for “red”. That’s certainly the origin of the name “Cochrane”.
If I may indulge in a moment of nostalgia…
In high school, our rowing team–with the encouragement of the coach–made shirts for themselves which read “Stroke 'til your cox can’t take it!” and wore them to school.
That was a short-lived experiment.
Our House Master was F. Skiddy von Stade, so, of course, we were named “Skid’s Rowers.”