Jessie's Arbok was most likely Jessie's first Pokémon. She got it as a Ekans for her birthday. Eventually it evolved into an Arbok because Jessie wished desperately for it to. It was later released to protect a group of Ekans from a Pokémon Poacher. When Jessie told it to stay behind and protect the Ekans, it started crying.
Note: Bite was classified as a Normal-type move at the time of its first usage.