The word 'pumpkin' is a free base element.
Self-proclaimed experts in the Facebook groups read the Etymonline entry and concluded that the word is <pump + kin>, with the same diminutive suffix you see in napkin, lambkin, or catkin. They are wrong.
Allow me to explain.
Hey, Punkin'
Your Facebook groups still do not understand this basic premise: You. Must. Have. Etymological. Evidence. For. The. Morphemes. You. Posit. Even in pumpkin.