I felt it may be both fun and educational to learn what some common utterances really mean. Hope all like this one.
What is the origin of that word or phrase? For example, the first one is:

Working the Graveyard shift

This refers to the attendants who monitored graveyards during the 1800's. They listened for bells attached to caskets in case the buried awoke. The could notify the attendant they were alive.

nursery rhyme

ring a ring rosie, a pocket full of posie
atishoo, atishoo, we all fall down.

from Middle Ages -- people carried a pocket of herbs to ward off the BlackPlague.

Cool penny

dead ringer

In association with the graveyard shift ( from post 1): if the attendant heard the bell ringing,then they had a dead ringer to deal with.

Dog-day

We had another dog-day afternoon at work today

from when Sirius, the Dogstar, rises with the sun---wrongly supposed to be when dogs are succeptible to
hydrophobia (rabies=madness)

and my last one in this group

Saved by the Bell

Well if the attendant working the graveyard shift, actually saved the deadringer, welll then you were Saved by the Bell

honeymoon

It was thought that if newlyweds drank mead (a wine made from honey) every evening for one month (the cycle of one moon) they would surely have a male heir in that year. That one-month period is called the ‘honeymoon.’

He was drooling like PAVLOV'S DOG at the thought of food


Ivan Petrovich Pavlov (1849-1936) a Russian physiologist studied digestion and "conditioned" or acquired reflexes. He rewarded a dog with food when the bell was rung. Eventually the dog would salivate at the sound of the bell with no food in sight.

'The whole nine yards'

This term referred to a 9 yard long machine gun ammo belt in WW1. To fire it until empty meant going the whole nine yards.

Tennis 15-love (zero)

It seems to have been adapted from the phrase "to play for love (of the game)" that is to play for nothing

from AskOxford.com OED

Teddy Bear

This term cme about in 1902 when President Theodore "Teddy" Roosevelt was hunting. The object game wasn't present and the guides brought him a stunned bear cub to finish. Roosevelt declined this unsporting solution and spared the animal. The next day the act of mercy was cartooned in the Washington Post. A New York candy store owner, Morris Michtom, saw this and asked his wife to sew up a Teddy Bear to put next to the cartoon in his window. Everyone wanted one. Within a year they sold so may they closed the candy store and opened the Ideal Novelty and Toy company, now one of the largest in the world.

Lukewarm


back to the 14th century the word luke seems to be an alternative form of lew (Old English, hleow)
meaning tepid

Cut to the chase

Cut to the chase means to get to the point without wasting time. The phrase originated from early silent films. Such films, particularly comedies, often climaxed in chase scenes. An inexpert screenwriter or director, unsure how to get to the climax, would just make an abrupt transition, known as a cut or jump cut.

The Bees Knees

this had no anatomical connection but instead originated from the phrase "The be all and end all" shortened to "the Bs and Es" and with a slippery tongue "the bees knees".

Midas touch

Some wealthy people are said to have the Midas touch.

from Greek mythology-- King Midas was known for his ability to turn into gold, all that he touched. This included his food. When he realized that he'd made a bad choice he asked the gods to be delivered from this gift and ultimately starvation.

Kissing cousins is a term understood in a number of ways, including:

Cousins who know each other well enough that they greet with kisses.

Cousins who actually marry each other; There are many famous cousin couples, for example Queen Victoria of the United Kingdom and her consort Prince Albert. There are several cousin-marriage support and advocacy web sites. In some jurisdictions this would be considered illegal as incest.

Cousins who are related not by blood but by virtue of being part of the same extended family (i.e. cousins by marriage but not marriage to each other). For example, if Alice and Brenda are cousins, and Alice marries Charles, then by this definition Charles and Brenda become kissing cousins; this despite the fact that Charles is already married.