A more thorough explanation:

unum quid

Unum quid is a Latin phrase that means "one thing." In history, this phrase was used to refer to a group of items that were considered as one, such as a set of glasses.

• A set of six glasses was considered as unum quid, or one thing, when sold together.
• When a person inherited a collection of books, they were often considered as unum quid, or one thing, and sold as a set.

These examples illustrate how unum quid was used to refer to a group of items that were considered as one for a specific purpose, such as selling or inheritance.