"person who receives guests," especially for pay, late 13c., from Old French oste, hoste "guest, host, hostess, landlord" (12c., Modern French hôte), from Latin hospitem (nominative hospes) "guest, stranger, sojourner, visitor (hence also 'foreigner')," also "host; one bound by ties of hospitality."

This appears to be from PIE *ghos-pot-, a compound meaning "guest-master" (compare Old Church Slavonic gospodi "lord, master," literally "lord of strangers"), from the roots *ghos-ti- "stranger, guest, host" and *poti- "powerful; lord." The etymological notion is of someone "with whom one has reciprocal duties of hospitality" [Watkins]. The biological sense of "animal or plant having a parasite" is from 1857.

early 13c., "inn, house of entertainment," from Old French ostel, hostel "house, home, dwelling; inn, lodgings, shelter" (11c., Modern French hôtel), from Medieval Latin hospitale "inn; large house" (see hospital). Obsolete after 16c., revived 1808, along with hostelry by Sir Walter Scott. Youth hostel is recorded by 1931.

1640s, "public official residence; large private residence," from French hôtel "a mansion, palace, large house," from Old French ostel, hostel "a lodging" (see hostel). The sense of "an inn of the better sort" is recorded from 1765. The same word as hospital.

1873, from hospital + -ize. "Freq[uently] commented on as an unhappy formation" [OED]. As verbs, hospitate is recorded from 1620s as "to lodge or entertain, receive with hospitality" but is rare; hospitize is from 1895. Related: hospitalized; hospitalizing.

early 14c., from Old French ospitalier "one devoted to the care of the sick and needy in hospitals;" see hospital.

formerly also hosteler, late 14c., "one who tends to horses at an inn," also, occasionally, "innkeeper," from Anglo-French hostiler, Old French ostelier, hostelier "innkeeper; steward in a monastery" (12c., Modern French hôtelier), from Medieval Latin hostilarius "the monk who entertains guests at a monastery," from hospitale "inn" (see hospital). Compare ostler.

district east of London, famed by early 19c. for the refugee Huguenot weavers who took up residence there; named for St. Mary Spital, from spital, a Middle English shortened form of hospital (q.v.) attested by late 12c. in names, sometimes also spittle, hence spittle-man "one who lives in a hospital;" spytel-house "hospital building."

Proto-Indo-European root meaning "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" [Watkins]. But as strangers are potential enemies as well as guests, the word has a forked path.

The word ghos-ti- was thus the central expression of the guest-host relationship, a mutual exchange relationship highly important to ancient Indo-European society. A guest-friendship was a bond of trust between two people that was accompanied by ritualized gift-giving and created an obligation of mutual hospitality and friendship that, once established, could continue in perpetuity and be renewed years later by the same parties or their descendants. [Calvert Watkins, "American Heritage Dictionary of Indo-European Roots"]

It forms all or part of: Euxine; guest; hospice; hospitable; hospital; hospitality; hospodar; host (n.1) "person who receives guests;" host (n.2) "multitude;" hostage; hostel; hostile; hostility; hostler; hotel; Xenia; xeno-; xenon.

It is the hypothetical source of/evidence for its existence is provided by: Greek xenos "guest, host, stranger;" Latin hostis, in earlier use "a stranger," in classical use "an enemy," hospes "host;" Old Church Slavonic gosti "guest, friend," gospodi "lord, master;" Old English gæst, "chance comer, a stranger."