History:

Families likely moved for better jobs or land, carrying this surname with them. While less important, forced moves due to things like political problems or land disputes might have also happened. These gradual shifts, both voluntary and involuntary, spread this surname across different places.

Description:

A simpler spelling, like "Teran," is easy to imagine. Adding a suffix—think "Teronson"—is another option, though Ive made that one up. Lastly, a shorter version, like "Terry," could exist, but its less common as a full surname.