semantic drift
Definition - The historical evolution of word's meaning. The word "drift" implies that it is drifting away from it original moored concrete sense towards great abstraction

Example -
The word-meaning evolution of the word silly moved from "blessed," to "pious," to "innocent," (c. 1200 CE), to "harmless," to "pitiable," (late 13c.), to "weak" (c.1300), to "feeble in mind, lacking in reason, foolish" (1570s).

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