Analysis of information sources in references of the Wikipedia article "Tiller" in English language version.
Rudder and helm. Orders to the helmsman were traditionally given in terms of 'helm'. That is to say, the position of the tiller rather than the rudder. 'Hard a-starboard!' meant 'put the tiller (helm) to starboard, so that the ship may go to port!' It will be realised that not only the bow turned to port, but also the rudder, [and] the top of the wheel...
Helm orders used to apply to the tiller but after the First World War began to be accepted and related to the rudder.
On 1 January the "direct" system of helm orders came into use on all British vessels. For centuries the order to "Starboard the helm, Port the helm" has caused the ship's head to go in the opposite direction, the practice having come down through the centuries when tillers were in use. Under the new regulations the order "Starboard" will be given, when it is intended that the wheel, the rudder blade and the head of the ship should go to starboard, and the order "port" will be given when it is intended that the wheel, the rudder blade and the ship's head should go to port. Though it is expected that little difficulty will be experienced in changing over from the "indirect" system to the "direct" system, for a time the orders will be given in the words "Wheel to Starboard" and "Wheel to Port" thus enabling the helmsman to adapt himself gradually to the new system.
On 1 January the "direct" system of helm orders came into use on all British vessels. For centuries the order to "Starboard the helm, Port the helm" has caused the ship's head to go in the opposite direction, the practice having come down through the centuries when tillers were in use. Under the new regulations the order "Starboard" will be given, when it is intended that the wheel, the rudder blade and the head of the ship should go to starboard, and the order "port" will be given when it is intended that the wheel, the rudder blade and the ship's head should go to port. Though it is expected that little difficulty will be experienced in changing over from the "indirect" system to the "direct" system, for a time the orders will be given in the words "Wheel to Starboard" and "Wheel to Port" thus enabling the helmsman to adapt himself gradually to the new system.
the Second Officer gives the order 'hard a starboard' ... the helmsman then turns the wheel and the ship to port. Steering orders used to be given as helm orders; as though the helmsman at the wheel was actually holding a tiller. So 'hard a starboard' would mean 'put your helm or tiller hard a starboard'. This would turn the ship's rudder to port and so the ship would turn to port
