Simplify the following text for a Grade 9 native English-speaking person.
Original: Philosopher Ludwig Wittgenstein first applied the term to redundancies of propositional logic in 1921 ; it had been used earlier to refer to rhetorical tautologies , and continues to be used in that alternate sense today .
Simplified: The philosopher Ludwig Wittgenstein first applied the term to propositional logic in 1921 .