Karl W. Randolph: While there were no elephants in Israel, archeological finds show that ivory was known and used as a decorative item in many places where elephants were not found. In other words, the ivory trade goes way back.

Yitzhak Sapir: The reason one would argue that it is ivory is that the word is easily analyzed as a compound -- $n and hbym. The first is the term for ivory elsewhere in the Bible including v. 18 of this chapter. The second is very similar to Yeb, the Egyptian name for Elephantine, as well as ?bw, the Egyptian word for Elephant. Perhaps it is also possible to draw a connection with the root ybb, which in Hebrew means lamentation of some form. Onqelos translates the sound of a shofar with this term in Num 10, and this seems to be very much parallel to the trumpet sound of an elephant. A shrill cry very much like a trumpet might also translate the word when it appears in the Bible as in Judges 5. The ancient translations also seem to translate this phrase - "teeth of an elephant."
Rather, I would suggest that the verse be broken up as so: zhb wksp [w]$n / hbym wqpym wtkyym In other words, the verse originally spoke of both ivory and elephants, and it was only later when the word hb as "elephant" was so antiquated that it remained only in the frozen term $nhb that it was reinterpreted in this verse with this meaning.