So why do contemporary grenades look like pineapples? I assumed–and apparently I’m not alone–that the raised pattern on the outside of the grenade was designed to increase the fragmentation capabilities of the grenade. According to Wikipedia, that is not accurate:
The Mills was a classic design; a grooved cast iron “pineapple” with a central striker held by a close hand lever and secured with a pin. According to Mills’ notes the casing was grooved to make it easier to grip and not as an aid to fragmentation, and in practice it has been demonstrated that it does not shatter along the segmented lines.