Why did the phrase punctus contra punctum become associated with counterpoint?

The phrase punctus contra punctum became associated with counterpoint because it literally translates to "point against point," which refers to the "note-against-note" style of composition used in early organum.1

In Medieval Latin, the term punctus referred to a musical note or the act of pricking, while contra meant against. During the Middle Ages, early polyphonic music was often written in a style where an accompanying voice was composed one note at a time to ornament or color each note of a plainchant melody. Because this technique involved aligning individual notes against one another, it was described as punctus contra punctum, a phrase that eventually evolved into the English word "counterpoint".21