According to Wikipedia,
The myth of the Coco originated in Portugal and Galicia. According to the Real Academia Española, the word coco derives from the Galician and Portuguese côco, which referred to a ghost with a pumpkin head. The word coco is used in colloquial speech to refer to the human head in Portuguese and Spanish. Coco also means “skull”.
Many Latin American countries refer to the monster as el Cuco. In Northern New Mexico and Southern Colorado, where there is a large Hispanic population, it is referred to by its anglicized name, “the Coco Man.”
In fact, I have heard the Coco Man invoked to either scare children or to relate just how scary the idea of the Coco Man is to a fully-grown adult who has been raised under the stern influence of a boogeyman that will come to get you if you’re bad, and maybe even if you’re good.
The idea of the Pumpkin Head now meshed together with El Cuco sends a shiver down my spine.
I had originally ascribed the idea of pumpkin heads as some sort of farm spirit that had gained autonomous movement (Read my account of seeing pumpkin heads), but now I’m going to have to re-examine that line of thought.
I am also thinking about one of the local gestures of either extreme dislike or a male full-arm and hand greeting gesture with somewhat “affectionate” undertones, especially between young men who are friends. The position of the hand suggests helping someone to give the gesturer a blowjob, but since the gesture means “skull,” it suggests servitude until death, “you’re my bitch even in death,” etc.
I’m really not sure how all these symbolic ideas fit together, but somehow, I think they are related.