What Does 'Long In The Tooth' Mean?

It comes from the world of horses.,say a person was looking to sell a horse,one of the first things the potential buyer would do is look into the horses mouth ,because the length of the animals molars indicates the age of the animal to the knowing eye.the longer the teeth the older the animal.these days its often used as a reference to us older humans----he/shes getting a bit  long in the tooth!   Another old adage we sometimes hear is ,,never look a gift horse in the mouth,,or in other words its free,just take it.which of course is a  saying directly  related to above.bye

It is an ancient folk phrase. It means to be old or aged and elderly. If a person has passed his prime and ripened in his old age then he/she is said to be over the hill or long in the tooth. This expression is derived from horses. It is a fact that the gums of a horse's mouth starts receding as they grow older and thus their teeth appear to have grown longer. Thus it is a common practice to have a look to examine the teeth of a horse to determine its age and thereby its value before buying it.

To be long in the tooth means to be getting on in the years. This phrase was first noticed in the English language during the 19th century though it might be possible that it has existed even before that but wasn't recorded until the mentioned century. It precedes another idiom, "don't look a gift horse in the mouth".

Long story short, it means that whomever it is directed at is old.