季氏 is short for
季孙氏, one of the three noble houses that ran the state of Lu in Confucius's day while its duke kept only the title. Book 16 is named after its opening words
季氏将伐颛臾 'the Ji clan was about to attack Zhuanyu', where Confucius rebukes two of his disciples who served the clan. The same passage gives
不患寡而患不均 'worry not about having too little, but about sharing it unevenly'.
