The authors agree that this is a Sicilian surname of dialect origin, linked to the term designating the conger eel, an elongated sea fish similar to the eel. E. Rossoni places it specifically in the Messina area, with a particular presence in Scaletta Zanclea, and notes that the etymon could be the dialect word grungo, used both to refer to the conger and, figuratively, in the sense of "exaggerated". He adds an alternative hypothesis: that the surname derives from a dialect alteration of the ancient Greek krounos —"jet of water, spring"—, which would indicate that the founding ancestor lived near a spring.

V. Blunda specifies that the original dialect form is grùncu and focuses on its belonging to the vocabulary of coastal fishing. He proposes that the nickname may have arisen to designate a fisherman specialized in catching this fish, or else as a physical comparison alluding to the elongated, slippery figure of the animal.