xyston

The story

1. substrate · derived from
2. Proto-Indo-European · derived from*ǵʰasto-
3. Ancient Greek · borrowed fromξυστόν“spear, javelin”
4. English todayxyston

Borrowed from Ancient Greek ξυστόν (xustón, “spear, javelin”), of unknown origin. Potentially from Proto-Indo-European *ǵʰasto- or *ǵʰasdʰo- (“branch ~ spear, sharp spine”, whence also gad, goad, and yard), but this is likely a substrate word in view of the various irregularities.