Why is a row in a periodic table called a period?

Answer 1

The properties of elements reoccur as the rows are repeated. Thus, the rows are called periods because each row results in a repetition.

Answer 2

A row in the Periodic Table is called a period because elements within the same row have similar chemical properties which repeat in a periodic manner. As you move across a period, the number of protons and electrons increases, leading to similar trends in the elements' properties.