I remember reading that God chose to rename Abram and Sarai by adding "heh" to their names, this letter being particularly holy because it appears twice in God's name. They became AbraHam and SaraH. Likewise, Yonatan can become Yehonatan and Yoram Yehoram, as a way of injecting a bit of the essence of God in the person.
Can you help me track the reference? And why name a boy Yonatan instead of Yehonatan?