Albert Barnes Commentary 1 Kings 9:18

"and Baalath, and Tamar in the wilderness, in the land," — 1 Kings 9:18 (ASV)

Tadmor - The Hebrew text here has "Tamor" (or "Tamar") as it is written, and "Tadmor" as it is traditionally read. That the latter place, Palmyra, was the one intended is apparent for three reasons:

1. The book of Chronicles distinctly states that Solomon built Tadmor (2 Chronicles 8:4), and it is improbable that this fact would be omitted in Kings.
2. It is highly likely that Solomon, with his expansive commercial vision, would have seized and fortified the Palmyrene oasis.
3. The ancient versions of the text are unanimous in translating "Tamar" here as "Tadmor."

It seems probable that Tamar was the original name of the place, as it is the Hebrew word for "a palm," from which it is generally agreed the town derived its name. Tadmor was likely a corrupt or dialectal variation of the word that was adopted at the city itself and eventually prevailed over the original name.

No reference to Tadmor is found in the Assyrian inscriptions or in any classical writer before Pliny.