those: [OE] Originally, those was the plural of this. It did not move across to that until the Middle English period, gradually replacing its previous plural thō. The game of musical chairs was completed by these, which was a new formation based on this. => this[those etymology, those origin, 英语词源]
c. 1300, Midlands and southern variant of Old English þas, nominative and accusative plural of þes, þeos "this" (see this). A collateral form of these, now used as the plural of that.