Why Do We Say That?

AM I MY BROTHERS KEEPER?
Like many old sayings in the English language this one came from the Bible. In Genesis Cain murdered his brother Abel. God asked Cain 'Where is your brother?' Cain answered 'I don't know. Am I my brothers keeper?'

TURN OVER A NEW LEAF
This means to make a fresh start. It means to turn over a page of a book.

HAVE NO TRUCK WITH
Truck originally meant barter and is derived from a French word 'troquer'. Originally if you had no truck with somebody you refused to trade with him or her. It came to mean you refused to have anything to do with them.

TOUCH WOOD
In Celtic time's people believed that benevolent spirits lived in trees. When in trouble people knocked on the tree and asked the spirits for help.