immutable

Etymology

From Middle English immutable, from Latin immūtābilis (“unchangeable”); im- + mutable.

adj

1. Unable to be changed without exception.
   The government has enacted an immutable law.
   In the trustless cryptocurrency world, you can still trust the cryptocurrency community and its mechanisms to ensure that the blockchain contains an accurate and immutable—unchangeable—record of cryptocurrency transactions. 2019, Peter Kent, Tyler Bain, Cryptocurrency Mining For Dummies, John Wiley & Sons, page 30
2. (programming, of a variable) Not able to be altered in the memory after its value is set initially.
   Constants are immutable.

noun

1. Something that cannot be changed.