Why do we say Port and starboard?

Early English boats were built like large canoes, (influenced by the Vikings dragon ships) which didn't have rudders. Most sailors were right handed so steering the boat was done by swinging a steering paddle or oar over the right side.

boat builders would fasten two pegs into the top strake of the boat, near the back on the right side. The steering oar would then be placed between the two pegs and secured with leather (simple rudder).

The sailors using these boats would lean on the top strake on the left side ( larboard), and steer from the right so sailors began calling the right side strake as the steering board or Starboard in early english'

Since these boats had big steering Oars on the right side it was much easier to tie the boat up on the left side. Supplies had to be "ported" (carried by a porter a person employed to carry supplies) so the port side comes from the word "porter"

‘The left side of the ship is called port, by Admiralty Order, in preference to larboard, as less mistakable in sound for starboard’

This is why we use the word Port as a place for cargo to be loaded and unloaded, as in returning to port.

This terminology became official in1844 for the British Navy and 1846 for the U.S. Navy.