This is an original Polynesian War Club (apa'apai) believed to be of Samoan or Tongan origin. Diamond-shaped or faceted four-sided head, rounded handle towards the pommel or butt. Made of very hard wood intended to inflict damage but not splinter or otherwise sustain damage in the process. These are sometimes referred to as "paddle clubs" but this one is short in comparison to the normal length.
The dimensions on this example are as follows: Overall length is ~19-1/2"; head width is ~3"; handle with is ~1-3/8"; head facets average ~1-1/2".