The American spelling: to turn into a fossil through natural processes, or to keep something exactly the same and unable to change.
From fossil (Latin fossilis 'dug up') + -ize (Greek -izein). The suffix -ize spread through American English influenced by Greek and Latin scientific terminology.
The metaphorical use of 'fossilize' to mean 'become outdated' is so powerful that scientists sometimes use it to describe organisms that haven't changed much—like coelacanth fish that look identical to their ancestors from 66 million years ago!
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