Lem actually mentions that at some point... while I don't have my copy of Peace on Earth with me, there's that scene where Tichy's picking out postcards and drawing sketches on them. He draws a mouse on a postcard with an owl and says something along the lines of "And how does a mouse behave around an owl? It is quiet, quiet as a mouse." and then comments on his name.
Lem actually mentions that at some point... while I don't have my copy of Peace on Earth with me, there's that scene where Tichy's picking out postcards and drawing sketches on them. He draws a mouse on a postcard with an owl and says something along the lines of "And how does a mouse behave around an owl? It is quiet, quiet as a mouse." and then comments on his name.