The word for today is…
ossify (verb):
1 : to change into bone
2 : to become hardened or conventional and opposed to change
Source : Merriam -Webster
Etymology : The skeletons of mammals originate as soft cartilage that gradually transforms into hard bone (in humans, the process begins in the womb and continues until late adolescence). English speakers have referred to this bone-building process as ossification since the late 17th century, and the verb ossify appeared at roughly the same time. English speakers had begun to use both ossification and ossify for more figurative types of hardening (such as that of the heart, mind, or soul) by the 19th century. Both words descend from the Latin root os, meaning “bone.” Os is also an English word that appears in scientific contexts as a synonym of bone, and the Latin term is an ancestor of the word osseous, which means “consisting of or resembling bone.” The superficially similar word, calcify, only refers to the deposit of calcium salts in soft tissue and is not synonymous with ossify.
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