Although the OP's question has already been answered, I'd like to catch the opportunity to elaborate on the specifics of the tillerman word.
- True, tiller is the farmer who tills the land.
- True, a tiller is the lever that operates the rudder on a small watercraft.
- True, in the US a "tillerman" is the man who steers the rear wheels of a fire truck.
But there is a lot more to it. We can trace back the story (if not the word itself) thousands of years ago. Here is how I see it.
Tillerman as farmer
Lets start with the origin of till in English.
As reliable as ever, the OED points us in the right direction: the word till is to be traced back to Middle English þylle, thyl or thyll and is the
"The pole or shaft by which a wagon, cart, or other vehicle is attached to the animal drawing it, esp. one of the pair of shafts between which a single draught animal is placed."
Various Germanic languages (and even non Germanic ones) have cognates of þylle, the general meaning of which seems to be that of a crafted piece of wood. Here are a few of them:
- In German Diele (plank) => dielen (to plank).
- In Old English, þilian is "to plank" (source)
- In Old Norse þilja (plank, deck) => wich gave Middle French Tille (smaller compartment in a box) => hence our cash till and tillac (deck of a boat in French)
- Icelandic þilfar (deck)
Here is a picture of a Bohuslän carving showing a farmer tilling his land. Please note that this place is at the heart of the Götaland (the German people Urheimat) and is of the Nordic Bronze Age (1700-500BC). Similar petroglyphs are also actually found in the South East of France (Mt Bego).
Tillerman as helmsman
If one accepts that þilja is a plank of wood then it is easy to understand that it can be used as a primitive rudder.
And the person who holds it is the... tillerman of course.
Here is a Viking example next to an older representation from the same bronze age site.
Tillerman as tiller-ladder operator
More recently, in the US, a tiller became a kind of
plough plow either pulled by an animal or even operated by a single man tilling his land.
Later still as fire engines became ever larger they were designed with directional rear wheels so that they could take more acute inner angles. To operate these rear wheels, you needed a second driver at the back of the trailer who had his own steering wheel and would make sure the rear wheels would follow in the front wheels tracks.
Here is an example. You can see the rear wheels in a different direction than the trailer itself.
The analogy with the tiller-farmer is quite obvious if you think of these farmers sitting on top of their tillers and also trying to take hairpin turns from one furrow to the next.
In non Germanic languages
Funnily enough there is another very similar situation occuring with romance languages.
In Latin, the pole in front of the plough used to be called the temo.
This word followd several paths.
- Le timon in French is the tiller (the shaft between the two oxen/horses).
- Le timon in French and Spanish is the rudder wheel (hence the timonier, the helmsman).
- El timon in Spanish is now the steering wheel.
May be there is a deeper link than one can see for now.
However, at least for Latin I can think of two words that could be related to the germanic þylle (reputed unexplained etymologies)
- talea (cutting, thin piece of wood [de Vann 2008], scion),=> Italian Talea. A tiller being also a sapling.
- telum (javelin, spear).