Pillar. The notion of a pillar is of a shaft or isolated pile either supporting or not supporting a roof. But, perhaps, the earliest application of the pillar was the votive or monumental. This, in early times, consisted of nothing but a single stone or pile of stones. Genesis 28:18; Genesis 31:40; etc.
The stone Ezel, 1 Samuel 20:19, was probably a terminal stone or a way-mark. The "place" set up by Saul, 1 Samuel 15:12, is explained by St, Jerome to be a trophy. So also, Jacob set up a pillar over Rachel's grave. Genesis 36:20.
The monolithic tombs and obelisks of Petra are instances of similar usage. Lastly, the figurative use of the term "pillar," in reference to the cloud and fire, accompanying the Israelites on their march, or as in Song of Solomon 3:6, and Revelation 10:1, is plainly derived from the notion, of an isolated column, not supporting a roof.