The chief (Fr. Chef – the head) – the head of the team, the unit, the formation.
Now it’s a vernacular colloquial name of any boss.
The Chiefs SVG in the French army
In the French army, the word “chef” is part of the names of military ranks: the French army major is traditionally known as “chef de bataillon” or “chef d’escadron”. In Spain, its analogue is Jefe.