No, it’s a pun on silly. The position just left of the batsman (from the bowler’s point of view) is the silly point. (The position opposite this, to the right of the batsman, is the short leg.)
That’s what makes it a “purely silly” joke. It’s a joke about the silly point.
The Penguin Dictionary of Curious and Interesting Numbers lists 39 as the first non-interesting number:
“39 appears to be the first uninteresting number, which of course makes it an especially interesting number, because it is the smallest number to have the property of being uninteresting. It is therefore also the first number to be simultaneously interesting and uninteresting.”
The first integer not listed in the Dictionary is 43, so 43 is presumably the first uninteresting number that is not also interesting.
Search for “Movement charger” or “kinetic charger”. These things already exist. They hit the news cycle every few months.