‘Long in the tooth’ isn’t a phrase that is common everywhere, though it is still used in many places. Something that is long in the tooth is something that is old and has nearly outlived its usefulness. Wives might tell their husbands that the worn out shirt or shoes that the husband is reluctant to get rid of, “Honey, that shirt is really getting long in the tooth. Why don’t you go get a new one?” A husband might tell his wife, “Sweetheart, I know you love that sweater, but it is getting pretty threadbare and long in the tooth.”
This phrase has a simple history and it dates from when horses were ridden to get from one place to another, to pull wagons and buckboards, to pull a plow, or as beasts of burden, to carry things. In those times, horses were as important as cars and trucks are today. Buying and selling horses was an important business and people didn’t want to end up paying too much for what the horse was worth.
In today’s world, it is sometimes difficult for even a mechanic to tell if a used car has one or more worn parts that will need to be replaced soon. In the horse and buggy days, it was substantially easier.
To figure out the age of a horse, a person looks at their teeth. This also gives them an indication of the overall health of the horse. If a horse is getting old, as with humans, the gums begin to draw back from the base of the tooth. This makes the tooth appear to be longer than normal, so the horse is ‘long in the tooth’. The usefulness of the horse is coming to an end. A buyer would know that they shouldn’t pay top-dollar for the horse because the horse would soon need to be replaced, assuming that they knew that the age of the animal could be measured this way.
It is too bad that it isn’t quite as simple to tell when your car (or mower, computer, spouse, and so forth) is getting long in the tooth, huh?.