The answer is that nothing is:
nIX (synonym for nothing)
Explanation: You are from
as you use expressions like 'by Jove',
which reminds us of Jupiter/Jove, the Roman god.
As such, your calculator is a bit unorthodox.
It allows entry of pi (because you are a smart Roman who knows about such things, unlike most around you), as well as Roman numerals.
So on to your conundrum...
You know that pi r squared can be used to calculate the area of a circle. Again, you are quite smart. Now, you have a circular swimming pool of radius 3, and would like to know the area of said pool, to determine how many fish it will hold (your guests like to eat grapes and swim with fish). You pull out your Roman Calculator and happily punch in pi (which appears like a lowercase 'n' on the digital display) and multiply it by 3 squared.
Now Roman numerals do not have digits, so the calculator does the best it can; it returns the result as pi * 9, which of course renders again as that "n" followed by "IX". This is similar to an algebraic number like 9x, except it is 9pi, and the pi is in front. Putting pi in front is an anomaly of the Roman calculator, but perfectly legitimate given the commutative property of multiplication.
You study the output, eager to head to the fish store. Wait?! "nIX"? Nothing??? How can the area of the pool be nothing? The calculator seems to work fine. III times III is still IX. The wires are still connected. What could be wrong???
Baffled, you turn on your Roman computer and head to stackexchange to find out.