"Motsuもつ" refers to the innards of animals such as cows, pigs, and chickens, also known as "hormone".
In a broader sense, it signifies all types of innards. Organs like the liver and heart, which are red, are called "Akamotsu", while the stomach and intestines are termed "Shiromotsu".
Dishes made from motsu include "Doteyaki", which is pig's innards seasoned with miso, and "Motsunabe", a famous local dish from Fukuoka.