The function f(x) seems to be selective for words related to certain historical events, primarily those involving war, persecution, or controversial incidents (e.g., Nazis, Holocaust, and World War 2). In addition, the function shows some selectivity for words related to nationality or cultural groups (e.g., Japanese, Jews). The function produces relatively low values (closer to 0) for most other inputs, including common or obscure words and concrete or abstract concepts.