Wikipedia
Datu is the title for chiefs, sovereign princes, and monarchs in the Visayas and Mindanao regions of the Philippines. Together with Lakan ( Luzon), Apo in Central and Northern Luzon, Sultan and Rajah, they are titles used for native royalty, and are still currently used especially in Mindanao, Sulu and Palawan. Depending upon the prestige of the sovereign royal family, the title of Datu could be equated to Royal Princes, European dukes, marquesses and counts. In big barangays, which had contacts with other southeast Asian cultures through trade, some Datus took the title Rajah or Sultan.
The word datu is a cognate of the Malay terms ''Dato' '' or Datuk, which is one of many noble titles in Malaysia, and to the Fijian chiefly title of Ratu.
Proofs of Filipino royalty and nobility (Dugóng Bugháw) can be demonstrated only by clear blood descent from ancient native royal blood and in some cases adoption into a royal family.
Usage examples of "datu".
And--these, you see, are an imaginative and mystic race--they have discovered in me, they say, some strong physical likeness to the Datu Rajah Muda Mandi, whose name they venerate, and who died--'suddenly'--before I came into their lives.
He, by skill and tact, and by cooperation with an equally wise and skilful Sulu chief, Datu Harun al Rashid, arranged with the Sultan a treaty to stop futile bloodshed.
Thither came the old Chief, eager to pour out his tale and ready and glad to hear, to concede, and also to do anything on earth that his good friend Datu Wood might wish.
For its American officers had hurried away to a War--that distant War for which Datu Wood was making ready his tribes--and into their places, too, the little Filipinos stepped, with small hearts steeped in gall.
And when we knew that Datu Wood was coming back at last, our hearts were lifted up to Allah in praise.
Of these I cite but one--that of a datu of ancient descent, of high standing among his people and by them greatly respected.
With Datu Rajah Muda Mandi, I fought and worked to keep the peace for America.
He knew from the chart that the biggest island of the three in the Datu Amman Group lay that way.