from The Century Dictionary and Cyclopedia
- n. A crystalline, intensely bitter alkaloid, C14H25NO2, found in the leaves of Carica Papaya, the melon-tree of South America. It is a not very powerful poison affecting the heart, spinal cord, and respiration.
Sorry, no etymologies found.
While you say that papaya seeds are edible, I found a statement on the Internet noting that they contained a substance called carpaine and that it was not advisable to consume them.
I am not aware of concern about papaya seed consumption because of carpaine.
Effect of carpaine, a papaya alkaloid, on the circulatory function in the rat.