The term “immutable” is used twice in the KJV Bible…
Both occurrences are found in the book of Hebrews and they are translated from the same Greek root word – “ametatithemi” this word is made up of three parts:
1. “a” – not
2. “meta” – around,
3. “tithemi” – to set in place, to establish, to set forth
The idea is this… “immutable” means “to not be moved around”, “to not be transferred”, “to not be re-established”. It is describing an unchanging character, position, mission, and/or activity.
“Wherein God, willing more abundantly to shew unto the heirs of promise the IMMUTABILITY of his counsel, confirmed [it] by an oath: That by two IMMUTABLE things, in which [it was] impossible for God to lie, we might have a strong consolation, who have fled for refuge to lay hold upon the hope set before us: Which [hope] we have as an anchor of the soul, both sure and stedfast, and which entereth into that within the veil; Whither the forerunner is for us entered, [even] Jesus, made an high priest for ever after the order of Melchisedec. (Hebrews 6:17-20)