I was looking for something else and found the "serpent" is actually a crocodile.
qadash in hebrew
The author there thinks that given some ambiguity of the use of the word נָחָשׁ nachash (qadash means "holy" or "consecrate") could refer to any reptile generally.
However the Hebrew word
תַּנִּין taniyn while generally meaning crocodile, is used in some other interesting ways as well.
From what I can gather, the etymology of the two words provides some interesting information.
Nachash seems to derive from a Proto-Semitic word indicating a lion, as in the Akkadian "nēšu ša qaqqari", "snake" "chameleon", literally "lion of the ground". Whereas the word taniyn seems to have a root ultimately derived from the meaning of "underworld" in a reference to the force under the earth that causes earthquakes. Ancient people imagining earthquakes being caused by some great beast under the earth, then associated with perhaps sea-monsters (like the great sea-monster leviathan in Levantine mythology), but then used to describe the common crocodile.
Languages are interesting, because as languages evolve they continue to bear the interesting fingerprints of the thoughts and ideas of people from long ago. For example our English word "god" is ultimately derived from from an ancient Proto-Indo-European word that probably meant "to invoke" or "to pour libations for". Possibly originally used to indicate the spirits of recently buried dead. Whereas other Indo-European languages took the older *dyeu, meaning "to shine" or "sky" which evolved into the Latin word deus (and "Jupiter", literally from something like "dyeus phater", "sky-father"), the Greek word Zeus, and the Sanskrit daevas--though in the Vedic texts the daevas are hardly heavenly gods, but have instead become malevolent demon-like beings.
I don't know what validity there is to treating nachash as simply a general term for a reptile, but it is true that words have nuances and differences that change and evolve over time; though I think it's fairly safe to consider that the word as used in Genesis is referring to a snake specifically. And that is because snakes regularly, in the ancient near east, are associated with guile. In the Sumerian Epic of Gilgamesh, it is a snake that tricks the hero Gilgamesh into giving over his immortality--though in the story the snake while a guileful trickster is not depicted as completely evil; likely with the serpent as frequently seen as a symbol of both death and rebirth, the ancient symbol of the ouroboros (snake eating its own tail) being an example of this. This serpent symbolism can be seen outside of Genesis in the Bible, as God instructs Moses to erect a bronze serpent to be a symbol through which God uses to heal his people of serpent bites, and even the Lord Jesus taught that while we should be gentle as doves to also be wise as serpents. Obviously snakes aren't actually wise, but the symbolism that was common in the ancient world is employed here.
So, in Genesis, it is a serpent who is a trickster that robs Adam and Eve of their eternal life in the Garden through the eating of the fruit of the knowledge of good and evil. And Christian exegesis has understood this to be a reference to the devil, it is the devil--rather than just an ordinary snake--that has done this. The snake being a creature associated with cunning, craftiness, guile, and death. But the story in Genesis, as is often the case, while sharing semiotic features with myths and stories of the Ancient Near East, does so in ways which subvert the usual tropes: the serpent that tricks Adam and Eve into eating the fruit which gets them kicked out of the Garden is not also a benefactor, but is purely a malevolent figure whom God curses and promises to ultimately destroy through the offspring of the very woman the snake sought to destroy by his guile.
As Christians we know, from this, that this is the promise of Christ who would come and defeat the devil and restore and reconcile Adam's progeny--the entire human race--from sin and death to God.
It should not be considered an accident that our Lord's Passion began, also, in a garden, and that the instrument of our redemption was also a tree--His cross.
-CrpytoLutheran