Some sample entries:
TO BE STILL WET BEHIND THE EARS
To be naïve, inexperienced. `He will be no match for them; he is still wet behind the ears.' The phrase has its origin in children's neglect to dry themselves behind the ears.
TO GO DOWN WITH THE SHIP
To stay at one's post until the bitter end. There was a tradition that the captain should go down with his ship. When the Titanic sank (1912), both the captain and designer went down with the ship, although they were offered places in the life-boats. In modern times, the rule has been relaxed, and the captain is expected to be the last to leave the ship.
A WOLF IN SHEEP'S CLOTHING
Someone who looks respectable and harmless but whose behaviour is quite the opposite. `Young children have to be aware of strangers who are kind and generous but could turn out to be wolves in sheep's clothing, such as paedophiles.' Also used with reference to trees, plants, food, etc. `Golden Rain is a magnificent-looking tree but it is like a wolf in sheep's clothing - the seeds are extremely poisonous.'
The Penguin Dictionary of English Idioms is well written and contains a wealth of knowledge. I would recommend it to anyone who wants
to improve their English.