The name has two competing readings and neither has won. Taken as sam-el it is the poison or venom of God; taken from a root meaning blind it is the blind god. Both are proposed by serious readers and the material does not settle between them, which is unusual, because most angel names in this collection are transparent.
The blind reading has one striking body of support outside Judaism. Several Gnostic texts, among them the Apocryphon of John and the Hypostasis of the Archons, give the demiurge three names, Yaldabaoth, Saklas and Samael, and gloss the last as the blind god. The figure they describe is a creator who fashions the material world in ignorance and declares himself the only god because he cannot see that anything exists above him. That is an extraordinary place for the name to appear, and it is independent of the Jewish material rather than derived from it.
Within Jewish literature Samael hardens over time. Late antique apocalyptic uses Sammael as a name for Satan outright. The Zohar and the Kabbalah that follows it set him at the head of the qlippoth, the husks or shells, and pair him with Lilith.
Western ceremonial magic inherited the name attached to Mars and had to do something with the reputation. Its solution was to read the severity as lawful rather than malevolent, the surgeon and not the murderer. That reading is coherent and it is also a choice, made late, against the weight of the older sources.