🔼The name Samaria in the Bible
The name Samaria (or rather: Shomron, which is spelled the same as the older name Shimron) was initially applied to a hill, which king Omri of Israel bought from a man named Shemer for two talents of silver (1 Kings 16:24). On top of the hill Omri built a city, which he generously named after Shemer, and he or his famous son Ahab moved Israel's seat of power there from Tirzah (1 Kings 16:29). Ahab's first order of business was to import the Sidonian princess Jezebel to Samaria, and build a temple for her deities Baal and Asherah (1 Kings 16:31-33). After Ahab's death, his son Ahaziah continued the practice, but the military captain Jehu killed Ahaziah and marched onto Samaria to destroy all pagan temples and massacre all associated priests and worshippers (2 Kings 10:25).
Allegiances to deities kept shifting, until in the ninth year of king Hoshea of Israel (722 BC), the Assyrians conquered Samaria (this name was now applied to the city, its environs and satellite towns) and deported the northern tribes (2 Kings 18:11). In order to repeople the abandoned cities of Samaria, the king of Assyria had initiated an international exchange program by bringing families from the northern regions of the realm to Canaan (2 Kings 17:24). That influx of foreigners (and their pagan theologies) threatened to dilute the now much fiercer nationalistic sympathies of the returning Jews, and both Ezra and Nehemiah embarked on vehement campaigns to refuse even the Israelites among the Shomronites access to Jerusalem and especially the restoration efforts (Ezra 4:2, see Ezra 10:10-11, Nehemiah 13:3). That in turn led to hostilities from the Samaritan side (although the authors claim that the initiative came from the Samaritans), and strained relations between Samaritans and Jews that lasted until well into the New Testamentary era (John 8:48).
The Oxford Companion to the Bible states, "Sometime after the arrival of Alexander the Great (332 BC), the Samaritans constructed on Mount Gerizim near Shechem a temple of Yahweh to rival Jerusalem's, but evidence from the Dead Sea Scrolls suggests that the definite religious break (the "Samaritan schism") between Samaria and Jerusalem, so apparent in the New Testament, did not occur before the Hasmonean period (second century BCE)".
Samaria was destroyed by Alexander the Great in 331 BC and rebuilt to Hellenistic designs. The Hasmonean leader Hyrcanus wrecked it again in 108 BC, but it was rebuilt around 50 BC by the Roman general Anulus Gabinius (who called it Gabinia). Herod the Great turned Samaria/Gabinia into a grandiose Roman city and named it after his emperor Augustus (which is Latin for glorious), namely Sebaste (which is Greek for glorious). It's probably noteworthy that the Bible never adopts any of the new names but keeps using the name Samaria and calls its citizens Samaritans.
🔼Samaria in post-Biblical times
Sebaste was sacked during the Jewish revolt of 66 AD, but revived and lasted until well into the Byzantine period. "It's now a wretched village, called Schemrun" according to the ever passionate reflections of Alfred Jones (Dictionary of Old Testament Proper Names; although he appears to copy John Parkhurst's slightly earlier Greek and English Lexicon to the New Testament). A 1983 tourist map of Israel that the Abarim Publications research team miraculously unearthed from our in-house library shows a village named Shomeron, right where Samaria must have stood. Next to it we find Sebastiya, and the whole region appears to be called Shomeron once again. Google Maps only shows the name Sebastia, cut through by route 5715. It has no Street View.
🔼The Samaritan and Jewish temples
The Samaritans built their Yahwistic temple on Mount Gerizim, and that was probably no accident. In Deuteronomy 11:29 and 27:12-13, Moses proclaims that upon entering the Promised Land, the Israelites would place a blessing on Mount Gerizim and a curse on Mount Ebal. By building their temple on Gerizim, the Samaritans seem to say that the Jewish temple was related to the other one, the one of cursing.
The two-hundred year old Yahwistic Samaritan temple on Mount Gerizim was destroyed in 110 BC by Hyrcanus. The (second or post-exilic) temple in Jerusalem was first expanded by Herod the Great around 20 BC and then destroyed during the Roman siege in 70 AD.
🔼Etymology of the name Samaria
The name Samaria comes from the verb שמר (shamar I), meaning to keep, guard, observe or give heed:
The name Samaria, or rather: Shomron, is formed by means of the familiar ון (waw-nun) extension, which personifies or localizes the root.
When king Omri bought the hill Samaria (or Shomron), he named it after the man he bought it from, namely Shemer. Shomron therefore literally means Shemer's Place, but it's reasonable to assume that to the locals the name Shomron quickly obtained the meaning of Place Of Watching, or something to that extent.
For a meaning of the name Samaria, NOBSE Study Bible Name List reads Watchtower and Jones' Dictionary of Old Testament Proper Names has A Watch Mountain.
BDB Theological Dictionary doesn't interpret Shomron beyond Belonging To Clan Shemer.