RuneScape Classic Wiki
The main RuneScape Wiki has an article on: King worm
The Old School RuneScape Wiki also has an article on King worm.

King worms can be pickpocketed from gnomes with 75 Thieving and found on the ground in the swamp near the Grand Tree. When consumed by themselves, they heal 2 Hits.

They are used in Gnome Cooking to create the worm-based foods.

See also