The only words Fuwamokotchi says when in baby form is Mama (マーマー), but after evolving it says Saa Kamukamu (サアー カムカム).
Fuwamokotchi's name comes from the two Japanese Onomatopoeia of fluffy. Fuwafuwa (ふわふわ) means fluffy like a whipped cream or a marshmallow, even bunnies. Mokomoko (もこもこ) means fluffy like a cloud or a cotton ball. Fuwamoko (ふわもこ) is often used to describe soft and fluffy clothing.