🔼The name Igdaliah in the Bible
The graceful name Igdaliah — which actually is spelled Igdalyahu, but in English transliterations we usually leave the final u away — occurs only once in the Bible.
The Lord instructs the prophet Jeremiah to bring the family of the Rechabites to the temple and offer them wine to drink. They refuse because their father Jonadab, son of Rechab, has instructed them to not drink wine, and so they haven't. Jeremiah is then to ask them, why they obey their earthly father but not their heavenly Father.
All this takes place in the chamber of the sons of Hanan, the son of Igdaliah, the "man of God" (Jeremiah 35:4).
🔼Etymology of the name Igdaliah
The name Igdalith consists of two elements, the final one being יה (Yah) = יהו (Yahu) = יו (Yu), which in turn are abbreviated forms of the Tetragrammaton יהוה, YHWH, or Yahweh.
The first part of our name is an expression of the verb גדל (gadel) meaning to become strong or great:
The letter י (yod) with which our name starts comes from the grammatical form that formally governs a future tense, but in translations usually is reflected by a present tense.
For a meaning of the name Igdaliah, NOBSE Study Bible Name List reads Great Is Yahweh and BDB Theological Dictionary has the similar Yah(u) Is Great. Jones' Dictionary of Old Testament Proper Names proposes The Lord Will Make Great.