arianayukiorginal
"I,was very young when I met Yoriichi". "He spared me when I was just a child".
"So Kamado Tanjiro will you promise me you'll defeate my father once and for all-
Chiyo Kibutsuji
Chiyo name means Thousand of Generations and Eternal this represents how he is supposed to live forever.
Muzan named him Chiyo after his own failure to save his mother from Yoriichi. Which she died at his hands.