Why is jellyfish called so?

The common name “jellyfish” is given to members of the phylum Cnidaria based on their gelatinous, nearly transparent body. The term "jellyfish" comes from the Portuguese and Spanish words "gelatina" and "pez", meaning gelatin and fish, respectively. Another common name for jellyfish is "sea jelly", alluding to their jelly-like consistency and marine habitat.