FROM THE HEART WITH GINI RIFKIN: Tale of a mule tail

In military terms a Shavetail usually refers to a Second Lieutenant who is not very experienced in Army matters.

The saying came from the practice in the army of shaving the tails of newly broken pack mules to distinguish them from seasoned ones. Good to know an animal's ability when you were singling one out from the herd.

Bell Sharps is another grading system,

and another whole fashion statement!

As the mules were trained and passed muster for performing various duties, their achievements were noted by again altering their tails. When needed, the soldier knew which animal to chose for which specific task.
One bell was a pack mule, two bells was pack and ride, three meant he'd pack, ride, and drive.

In this image, it appears the one on the left is training the one on the right as to the proper etiquette of driving.

Bell Sharps is not to be confused with Bellwether,

literally a whole different animal.

Originally, the bellwether goat would be the one to lead the other animals back to the barn at night. Today, a bellwether is a person who actively leads or establishes a trend that is taken up by others.

The word is formed by a combination of the Middle English words belle (meaning “bell”) and wether (a noun that refers to a male sheep or goat who has been castrated).This usage first appeared in English in the 15th century and has remained in the language ever since.