dog

dog a dog is the emblem of St Dominic, St Roch, St Eustace, St Hubert, and St Bernard of Aosta.

The nickname of Diogenes was the Dog.
dog and pony show an elaborate display or performance designed to attract people's attention (chiefly North American).
dog days the hottest period of the year (reckoned in antiquity from the heliacal rising of Sirius, the Dog Star (see below).
dog does not eat dog people of the same profession should not attack each other. The saying is recorded from the mid 16th century, but a similar idea is found in De Lingua Latina by the Roman scholar and satirist Varro ((116–27 bc), ‘canis caninam non est [a dog does not eat a dog's flesh].’
dog-eat-dog used to refer to a situation of fierce competition.
dog in the manger a person who is inclined to prevent others from having or using things that one does not need oneself, from the fable of the dog that lay in a manger to prevent the ox and horse from eating the hay.
a dog is for life, not just for Christmas the slogan of the UK's National Canine Defence League (now Dogstrust), introduced in 1978 with the intention of dissuading people from giving puppies as Christmas presents.
dog Latin a debased form of Latin; the term is recorded from the late 18th century, and represents a derogatory use of dog.
the dog returns to its vomit a pattern of unpleasant behaviour is likely to be repeated. The saying is recorded from the late 14th century, and is often used with biblical allusion to Proverbs 26:11, ‘As a dog returneth to his vomit: so a fool returneth to his folly.’
dog rose a delicately scented Eurasian wild rose with pink or white flowers, which commonly grows in hedgerows, the root of which was in classical times thought to cure the bite of a mad dog.
Dog Star the star Sirius. The name is a translation of Greek kuon or Latin canicula ‘small dog’, both names of the star; so named as it appears to follow at the heels of Orion (the hunter).
a dog that will fetch a bone will carry a bone someone given to gossip carries talk both ways; saying recorded from the mid 19th century.
dog-tooth a small pointed architectural ornament or moulding forming one of a series radiating like petals from a raised centre, typical of Romanesque and Early English styles.
every dog has his day everyone, however insignificant, has a moment of strength and power. The saying is recorded from the mid 16th century; a modern equivalent might be Andy Warhol's ‘famous for fifteen minutes’.
every dog is allowed one bite proverbial saying, early 20th century, based on the common law rule (dating from at least the 17th century) by which the keeper of a domestic animal was not liable for harm done by it unless he knew of its vicious propensities. If a dog had not bitten anyone before, a tendency to such behaviour could not have been known.
give a dog a bad name and hang him once a person's reputation has been blackened their plight is hopeless. The saying is recorded from the early 18th century. (Compare he that has an ill name is half hanged.)

See also black dog, dogs, a live dog is better than a dead lion, is thy servant a dog?, the tail wags the dog, you can't teach an old dog new tricks, there are more ways of killing a dog, a woman, a dog, and a walnut tree.