You're on a roll — In the context of compound interest:
The original principal is the initial amount of money invested or borrowed at the very beginning of the term. It is a fixed starting value.
The principal (or sometimes "current principal") refers to the amount on which interest is calculated in any given compounding period. In compound interest, this amount changes over time because the interest earned in previous periods is added to the original principal, becoming part of the new principal for the next calculation.
So, the original principal is the starting point, while the principal for subsequent calculations grows as interest compounds.
What's next?