Fennel
The Essentials

Fennel is the sweet, licorice-scented seed whose anethole gives it real carminative (traditionally used to settle gas and bloating) effect on gas. Small randomised trials also support it for primary dysmenorrhea, and — at low, professionally prepared doses — for infant colic.
A pinch chewed after a meal is a two-thousand-year Persian and Indian habit, and a safe one.
The culinary seed and bulb are broadly safe. The concentrated essential oil (the concentrated aromatic oil of the plant) isn't for internal use in pregnancy or in infants.
Fennel (Foeniculum vulgare) seeds have a sweet, licorice-like aroma. In Persian and Indian tradition, chewing fennel after a meal aids digestion and freshens the breath. Anethole, its main aromatic compound, has carminative (gas-relieving) effects.