I am trying to understand the relationship between an אַיִל (ram, Ovis canadensis) and אַיָּל (stag, Cervidae). According to scientific classification these are different families. They seem to share a common Hebrew root in the bible. Yet one is considered a domestic animal and the other wild. What is the reason for their shared shoresh (root)?
The same question could be possed regarding English animal names like buffalo or panther? Why did English-speakers apply the term buffalo to creatures of diverse scientific classification like the Bubalus bubalis and the Bison bison? Or why did English speakers apply panther to the scientifically distinct leopards, jaguars, and cougars (Panthera pardus, Panthera onca, and Puma concolor respectively)?
Scientific classification is a clean, zero-overlap system. Languages are messy, and they are changing. So were the words ancient Hebrew speakers used and how they applied them. In short, the answer is that's just how languages work. This might not be very satisfying, but it is true.