GUEST (a word common to Teutonic languages; cf. Ger. Cast, and Swed. giist; cognate with Lat. hostis, originally a stranger, hence enemy; cf. " host " ), one who receives hospitality in the house of another, his " host "; hence applied to a parasite.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)