Anchor cable was wrapped around posts called bitts. The last piece of cable was called the bitter end. If you let out the cable to the bitter end there was nothing else you could do, you had reached the end of your resources.
THE BLIND LEADING THE BLIND
In Matthew 15:14 Jesus criticised the Pharisees, the religious authorities of his day, 'they be blind leaders of the blind'.
ON YOUR BEAM ENDS
On a ship the beams are horizontal timbers that stretch across the ship and support the decks. If you are on your beam-ends your ship is leaning at a dangerous angle. In other words you are in a precarious situation.
In the past people believed that bees flew in a straight line to their hive. So if you made a bee line for something you went straight for it.
If you get something to boot it means you get it extra. However it has nothing to do with boots you wear on your feet. It is a corruption of the old word bot, which means profit or advantage.
COCK A HOOP
This phrase comes from a primitive tap called a spile and shive. A shive was a wooden tube at the bottom of a barrel and a spile was a wooden bung. You removed the shive to let liquid flow out and replaced it to stop the flow. The spile was sometimes called a cock. If people were extremely happy and wanted to celebrate they took out the cock and put it on the hoop on the top of the barrel to let the drink flow out freely. So it was cock a hoop. So cock a hoop came to mean ecstatic.