Simplify the following text for a Grade 12 native English-speaking person.
Original: While Celtic Reconstructionism was the earliest term in use and still remains the most widespread , as the movement progressed other names for a Celtic Reconstructionist approach were also popularized , with varying degrees of success .
Simplified: While Celtic Reconstructionism was the earliest name in use , and is still used the most often , other names for a Celtic Reconstructionist approach have also come into use , with varying degrees of success .