Senses
公公 father-in-law
husband's father
公公 old man
respectful form of address for an elderly man
公公 grandfather
one's grandfather or maternal grandfather
公公 eunuch
respectful form of address for a palace eunuch in former times
公公 Grand Tutor
(archaic) respectful form of address for a high official, such as a Grand Tutor 太师