On the old wooden navy ships, cannon balls were carried on brass holders called "monkeys". On a very cold day the brass would contract and the cannon balls would fall off, and it was said to be "cold enough to freeze the balls of a brass monkey"
Hence the phrase brass monkeys.
On old navy ships the plates that food was eaten off of were square. This was to aid storage and prevent them rolling abount in rough seas. The sailors were given two full meals a day, often called the "two square meals"
Old electric Trams were controlled by a rotary switch with notches cut in the panel for indication. To get full power (and speed) the tram had to be run on the top notch. Trams on good condition were described as being in "Top Notch" condition.
