The revers of square root is to square, which means multiple the number by itself. For example: the Square Root of 64 is 8 because 8 times 8 is 64.
The square root of a negative number results in "i" (meaning imaginary) because there is no real number that can be multiplied by itself to get a negative number. Two negative numbers multiplied equals a positive and two positive numbers multiplied equals a positive. The only way to get a negative number is to multiple a negative and a positive. But doing that goes against square roots because it has the be the same number. Imaginary numbers are like place holders for impossible combinations. Square root of 50 is 7.1. As soon as you make it negative you have to throw in "i" for imaginary.
