"hole or crevice through which one may peep or look," 1680s, from peep (v.1) + hole (n.).
Entries linking to peep-hole
peep v.1
"to glance, look from a state of concealment" (especially through or as through a small or narrow opening), mid-15c., pepen, perhaps an alteration of Middle English piken (see peek (v.)). Hence, "to come partially into view, begin to appear" (1530s). Peeping Tom "a curious prying fellow" [Grose] is from 1796 (see Godiva).
hole n.
Old English hol (adj.) "hollow, concave;" as a noun, "hollow place; cave; orifice; perforation," from Proto-Germanic *hulan (source also of Old Saxon, Old Frisian, Old High German hol, Middle Dutch hool, Old Norse holr, German hohl "hollow," Gothic us-hulon "to hollow out"), from PIE root *kel- (1) "to cover, conceal, save." As an adjective, it has been displaced by hollow, which in Old English was only a noun, meaning "excavated habitation of certain wild animals."
As a contemptuous word for "small dingy lodging or abode" it is attested from 1610s. Meaning "a fix, scrape, mess" is from 1760. Obscene slang use for "vulva" is implied from mid-14c. Golfing hole-in-one is from 1914; as a verbal phrase from 1913. To need (something) like a hole in the head, applied to something useless or detrimental, first recorded 1944 in entertainment publications, probably a translation of a Yiddish expression such as ich darf es vi a loch in kop.