In Fred Hoffman's book, Polish Surnames: Origins and Meanings, 2nd Edition, he says that Rzasa comes from the word rzasa, which means "plenty, abundance," also eyelash, duckweed."

According to the Slownik nazwisk wspolczesnie w Polsce uzywanych, "Dictionary of surnames in Current Use in Poland", published in 1992, there are 1687 people with the Rzasa name living in Poland.