Forms: … —OTeut. gasti-z: —WAryan ghosti-s, represented also by L. hostis, orig. ‘stranger’, in classical use ‘enemy’ (whence the compound hosti-pot-, contracted hospit-, hospes guest, host)…

—OED, Guest

Although the word is known only in the WGer. langs. (in all of which it is found with substantially identical meaning), it appears to be of pre-Teut. formation. The sense of the pre-Teut. ghoizdo-z, if the ordinary view of its etymological relations be correct, should be ‘fury, anger’: cf. Skr. hedas neut. anger, Zend zoizda- ugly; the root gheis- ghois- appears with cognate sense in ON geisa to rage, Goth. usgaisjan to terrify (see Gast v.); outside Teut. the derivatives seem to point to a primary sense ‘to wound, tear, pull to pieces.’

—OED, Ghost

The third corollary can also be political: it is what would make us pass, in spirit, from the hostage to the host/guest and from the host/guest to the ghost. (This is the series constituted by the hostage, host, guest, ghost, holy ghost, and Geist.)

—Jacques Derrida, Aporias