Why do we say it's a dog's life

A. As Johnjo explained, it means a totally miserable existence, where life treats you unfairly. Dogs often come off badly in well-known sayings.

Q. Such as
A. Dogsbody - a drudge who has to do all the menial work; dog tired - too exhausted to do anything but curl up and sleep; go to the dogs - to go to ruin; a dog's chance - no chance at all; black dog - used by Winston Churchill to describe his fits of depression, to name but a few.

Q. Why do dogs have such a bad reputation
A. The word 'dog' is often used to describe things which are thought of as inferior or worthless. For example, dog violets are similar to 'real' violets, but are scentless; dog Latin, which is when English words are treated like Latin for humorous effect; dog cheap, meaning very cheap indeed; and dog end - a cigarette butt.

Q. You know what they say - give a dog a bad name... But don't our canine friends have some noble qualities, too
A. Yes, and many of these are also reflected in sayings, such as 'top dog', the person who comes out on top; 'a dog with two tails' which refers to a happy dog's tail-wagging; and 'lie doggo' from a dog's ability to lie still but remain alert.

Q. Aren't they known for their ferocity...
A. Absolutely. The Dogs of War, the title of a Frederick Forsyth novel (1974) and subsequent film (1980) comes from Shakespeare's Julius Caesar - 'Cry havoc and let slip the dogs of war.' And the term 'dog eat dog' describes a situation where the competition is so fierce that people are prepared to harm each other in order to win.

...and their sheer 'doggedness'
Exactly - see 'There's life in the old dog yet', a phrase which is used to compliment one who may have been considered 'past it'. (It was famously used as the title of a painting by Sir Edwin Landseer, which shows a man rescuing a deerhound which has not plunged over a precipice - unlike a stag and two other dogs.)

...and their sheer lovability
Well, of course. And so a saying that has been attributed to Madame de Sevigne (1626-96), Madame Roland (1754-93) and Frederick the Great of Prussia (1712-86): 'The more I see of men, the more I love dogs.'

By Hermione Gray