Why does “Holiness to the Lord” appear on LDS temples? Was the phrase used on buildings anciently?

The Wikipedia article on LDS temples asserts that the phrase “Holiness to the Lord” was inscribed “on the Old Testament Temple of Solomon.” However, so far as we know, the phrase was never used as part of any ancient building. It is unique to modern temples. In this video, Jeff Bradshaw addresses three questions:

1. How did the practice of inscribing LDS temples with the words “Holiness to the Lord” begin?
2. What was the meaning of the phrase in the Old Testament?
3. What is the purpose of modern temples?

An article version of this video is available on the Interpreter Foundation at KnoWhy OTL26A — Why Does “Holiness To the Lord” Appear on LDS Temples?.