Easton's Bible Dictionary: M. G. Easton, M.A., D.D.
Occurring only in the title of Ps. 9. Some interpret the words as meaning "on the death of Labben," some unknown person. Others render the word, "on the death of the son;" i.e., of Absalom (2 Sam. 18:33). Others again have taken the word as the name of a musical instrument, or as the name of an air to which the psalm was sung.