'Certain' in the Bible

There was a certain man of Ramathaim-zophim, of the hill country of Ephraim, named Elkanah the son of Jeroham, the son of Elihu, the son of Tohu, the son of Zuph, an Ephraimite.

David said to Ahimelech the priest, “The king has commissioned me with a matter and has told me, ‘Let no one know anything about the matter for which I am sending you and with which I have commissioned you. I have directed the young men to a certain place.’

Now one of Saul’s servants was there that day, detained before the Lord; his name was Doeg the Edomite, the chief of Saul’s shepherds.

So look, and take note of all the places where he hides and come back to me with the established facts, then I will go with you. If he is [anywhere] in the land, I will search him out among all the thousands of Judah.”