grill : nm Un grill is a kitchen utensil formed by a metal grid placed above a hearth or cast iron plate allowing cooking over high heat.
Being on the grill, extremely anxious or impatient, being unpleasantly in the spotlight; to be in a situation where one is judged: interview, interview, questioning… (see below).
Putting / holding someone on the grill: worrying them; put pressure on him, question him.
The phrase “On the Grill”: Anxious or impatient - In a distressing or embarrassing situation.
Those who have ever had the opportunity to put their butt on the barbecue grill know how painful and embarrassing this situation is at the same time. And the others are perfectly capable of imagining it.
The image is therefore sufficiently meaningful that it does not really need to be explained.
This expression is found in 1740 in the Dictionary of the French Academy, with the first meaning cited which has therefore been reinforced over time to give the second.
According to the French linguist, lexicographer and writer Alain Rey (1928-2020), it could be an allusion to the martyrdom of Saint Lawrence who, in 258 in Rome, was burned on a grill by the prefect of the city during the reign of Emperor Valérien.