a simple misunderstanding
In Germany it is literally translated to grenade apple so you got a point
Well apple in french is "pomme" so "pomme grenade" is kind of the literal translation - not sure if the English word actually comes from this
According to Wikipedia:
The name pomegranate derives from medieval Latin pōmum "apple" and grānātum "seeded".[7] Possibly stemming from the old French word for the fruit, pomme-grenade, the pomegranate was known in early English as "apple of Grenada"