ע as a prefix?

I recently noticed that several animals mentioned in the Torah (the Old Testament), specifically the bat, mouse, scorpion, and spider, called עטלף ’atalef, עכבר ’akhbar, עקרב ’aqrav, and עכביש ’akavish respectively all start with an ע ’ayin, which is followed by three consonants. Is there some sort of pattern going on? These are all animals associated with impurity and creepy-crawly things, which was what piqued my curiosity. Is this ע some sort of a prefix? Do the three remaining letters correspond to a Hebrew root?
Well, the Koehler-Baumgartner Hebrew & Aramaic Lexicon suggests that עטלף stems from ע.ט.ף., meaning "to wrap," and imbuing עטלף with the meaning of "cloak-animal."
All the other ones seem to have cognates in sister semitic languages, making these words pretty old. Will we ever know? Anyway, I'm not satisfied. Nor should you be.