long in the tooth

To be long in the tooth typically means to be very old. As people age, their gums descend slightly and therefore their teeth appear to be longer. This is where the phrase long in the tooth originated as something or someone that is old in the matter of years they have been around or alive. Long in the tooth is an older phrase used in a lot of media like movies and television shows when describing someone is very old but they want to say it in a more creative way.