In the word ‘cell-phone’, what does the word ‘cell’ denote?

 A basic cell phone is a two-way radio, consisting of a radio transmitter and a radio receiver. When you chat with your friend on your cell phone, your phone converts your voice into an electrical signal, which is then transmitted via radio waves to the nearest cell tower.

A city or region is divided into different areas, each of which is called a cell. When you are in a particular cell, the tower in that cell transmits the signal.