PIE base ‘stranger, guest, host’, properly ‘someone with whom one has reciprocal duties of hospitality’, representing ‘a mutual exchange relationship highly important to ancient Indo-European society’. “But as strangers are potential enemies as well as guests, the word has a forked path.”

Other derivatives include guest, hospice, hospitable, hospital, hospitality, host ‘person who receives guests’, host ‘multitude’, hotel, hostel; hostage, hostile, hostility, xenophobia; and xenon, from Greek, neuter of xenos ‘strange’.

[Pokorny *ghosti-s, ‘stranger; guest’, pp. 453.]