Old English ure "of us, pertaining to or belonging to us," genitive plural of the first person pronoun, from Proto-Germanic *ons (source also of Old Saxon usa, Old Frisian use, Old High German unsar, German unser, Gothic unsar "our"), from PIE *nes-, oblique case of personal pronoun in first person plural (source of Latin nos "we," noster "our"). Also compare ours.
Ourselves (late 15c.) "we or us, not others," modeled on yourselves, replaced original construction we selfe, us selfum, etc. It often is added to we for emphasis.
"that or those belonging to us," c. 1300, oures, a double possessive (with genitive suffix -s (1)), originating in northern England, it has taken over the absolute function of our (q.v.). In Middle English ourn, ouren also were used.
Ours is a later possessive form from our, and is used in place of our and a noun, thus standing to our in the same relation as hers to her, yours to your, mine to my .... [Century Dictionary]
pertaining to a proposed meta-family of languages including Indo-European, Semitic, Altaic, and Dravidian, 1966 (Nostratian is from 1931), from Latin nostratis "of our country," from nostras "our countrymen," plural of nostrum, neuter of noster "our," from nos "we" (from PIE *nes- (2); see us).
c. 1600, "a medicine made of secret ingredients by secret methods," but commonly "quack medicine," from Latin nostrum remedium "our remedy" (or some similar phrase), presumably indicating "prepared by the person offering it," from Latin nostrum, neuter of noster "our," from nos "we," from PIE *nes- (2); see us. In extended use, "a pet scheme for accomplishing something" (1749).