From 2,500 to 2,000 B.C. "Pharaoh" originally mean "great house" (palace) but it gradually came to mean the king of Egypt who lived in there. See The Expositor’s Bible Commentary vol.2 p.288-289 and the Wycliffe Bible Dictionary p.1323-1325 for more info.
Kutoka mwaka 2,500 hadi 2,000 KK neno "Farao" kwa mara ya kwanza lilimaanisha "nyumba kubwa" (mahali) lakini lilibadilika polepole na kumaanisha mfalme wa Misri aliyeisha pale.