A number taken to the power 2 is said to be squared, so 
is called "
squared." This terminology derives from the fact that
the area of a square of edge
length 
is given by 
, hence the operation taking a square's edge length to its
area is known as "squaring" and the quantity 
derived from 
by squaring is known as "
squared."
Not that the term "squaring" also refers to the geometric construction, using only compass and straightedge, of a square which has the same area as a given geometric figure.
