The term originates from the French word stagiaire meaning trainee, apprentice or intern.
The individual completing this activity is referred to as a stage, stagiaire ([staʒjɛʁ]), commis (assistant chef) or volontaire ("volunteer").
Trialling is an activity often used to assess the skills and training of a cooking job candidate.
The hiring chef might assess the trial cook's adaptive skills in the new kitchen and how they interact with other staff in the restaurant.
Before the advent of modern culinary schools, young cooks learned their craft as unpaid apprentices in professional restaurant kitchens and bakeries (and other food preparation establishments: pastry shops/patisserie, butcher shops/boucherie, candy shops/confisserie, hotels, etc.)