Passing Phrase - www.learnhebrew.org.il
Literally: Tower of tooth
Idiomatically: Ivory tower
If you wanted to actually translate "Ivory Tower" from English to Hebrew, you would probably call it "Migdal Shinhav." The phrase is found referring to one of the palaces of King Achav (Ahab) (Kings I 22:39). The word "shen" refers to a tooth, but as you figured out by now, it is the tooth of an elephant. In Hebrew the word "shinhav" for ivory comes from a combination of the word shen (tooth) and the Egyptian word for elephant, "Hav."
As such, Achav's castle must have had lots of elements that were ivory. You can also find it in Song of Songs (7:4). Today it has a totally different meaning which dates to the mid-19th century. It refers to a place where people are happily studying or whatever, and are sheltered or isolated from the rest of us.
Recently, a professor gave a lecture in Haifa University called
"האקדמיה: מגדל שן או מגדלור?"
"Academia: Migdal shen oh migdal ohr?"
"Academia: An Ivory tower or a lighthouse?"
Of course the only people that came to hear it were from – you guessed it – Academia.