It is rumored that the ferocious warning markings on its belly differ from area to area.
– Pokemon Red/Blue Pokedex
Arbok is based on a cobra, and its name is “kobra” spelled backwards. Its English name is the same as the Japanese one.
In the anime, Jessie had an Arbok that she used for the first few seasons. It was an Ekans for the first few episodes, but evolved into Arbok quite early on. Despite losing to Ash and his friends all the time, Arbok seems quite happy and fond of Jessie. It left Jessie to protect a group of Ekans being hunted by poachers. It was quite reluctant to go, but Jessie sort of forced it to go. In the anime, Arbok says “charr-bok!”
Stat-wise, it has decent Attack and Speed, and one of its abilities Intimidate is useful. Starting Gen IV, it learns the three elemental Fangs at the start (which means you’d need Heart Scales to relearn them). It’s one of the few Pokemon to learn Glare by level-up.
Strangely enough, it’s in the Dragon egg group for some reason. The only way to get a Hydreigon with Dark Pulse is to teach the Dark Pulse TM to an Arbok in Gen IV, bring it to Gen V, and breed with Hydreigon.