Milk

Milk is a substance produced by mammals to feed their young. It is in fact the reason they're called mammals in the first place.

Uses

Most furry mammals are raised on this substance with the lactation of the mother giving nutrients and helping their immune and digestive systems develop.

Chronology

Snowdrop has a fondness for it given that it was a giving food, and reminded her of her own mother.<ref>Not that she’d really done much in the wild. She had been born, crawled her way to her mom’s pouch, and then her mom had stopped giving milk.
[...]
Milk was happiness and love. It was one of the only things that was a giving food, not a taking one. Meat was taken from dead animals, and sometimes, according to Gashwad, living ones, but she hadn’t tried that yet. Fruit was the closest thing she could think of, but according to Toadswallow, fruits and vegetables were sort of like the sex organs of plants. It was only sort of by weird design that they became delicious. Animals ate the plant’s private parts, sort of, then they crapped out seeds and the plants got to spread. Or the plants were made so they didn’t have seeds and it was kind of like eating a juicy dick with a condom on it, Toadswallow said. That conversation had moved on to how flowers were also sex organs of plants, and Snowdrop was named after a flower, so she was sorta named something rude. - Excerpt from Leaving a Mark 4.x</ref>

References