peep (v.1) Look up peep at Dictionary.com
"glance" (especially through a small opening), mid-15c., perhaps alteration of Middle English piken (see peek (v.)). Peeping Tom "a curious prying fellow" [Grose] is from 1796 (see Godiva).
peep (v.2) Look up peep at Dictionary.com
"make a short chirp," c.1400, probably altered from pipen (mid-13c.), ultimately imitative (compare Latin pipare, French pepier, German piepen, Lithuanian pypti, Czech pipati, Greek pipos).
peep (n.2) Look up peep at Dictionary.com
"short chirp," early 15c., from peep (v.2); meaning "slightest sound or utterance" (usually in a negative context) is attested from 1903. Meaning "young chicken" is from 1680s. The marshmallow peeps confection are said to date from 1950s.
peep (n.1) Look up peep at Dictionary.com
1520s, first in sense found in peep of day, from peep (v.1); meaning "a furtive glance" is first recorded 1730.