Webster's Revised Unabridged Dictionary · 1913

Your (ūr) , pronoun and adjective

[Old English your, your, eowr, eower, Anglo-Saxon eówer, originally used as the gen. of ge, gē, ye; akin to OFries. iuwer your, Old Saxon iuwar, Dutch uw, Old High German iuwēr, German euer, Icelandic year, Gothic izwara, izwar, and English you. r189. See You.]

The possessive takes the form yours when the noun to which it refers is not expressed, but implied; as, this book is yours. “An old fellow of yours.”