First of all, it's spelled Jan Lukasiewicz, with a `k'; also, there is a bar through the L. It's pronounced `Woo kah SHAY vich'.

Second, it is a common misconception that Lukasiewicz invented reverse polish notation. In fact, he did not; he invented what is known as Polish notation, a bracketless representation of propositional and predicate logic. In logic, Polish notation uses the following symbols:

RPN is called `reverse' because it was based on the preexisting Polish notation. Postfix (and prefix) notations for logic and arithmetic surely existed before Lukasiewicz; it was his notation, though, that gained the widest popularity.

In addition to RPN, Cambridge Polish notation (a parenthesised prefix notation, used in Lisp) is named after Lukasiewicz's Polish notation.

Lukasiewicz was also well-known for his work on three-valued logics---probably much more important in the long run than his particular usage of prefix notation.