mid-14c., "that is such by its essence," from Late Latin essentialis, from essentia "being, essence," abstract noun formed (to translate Greek ousia "being, essence") from essent-, present participle stem of esse "to be," from PIE root *es- "to be." Meaning "pertaining to essence" is from late 14c., that of "constituting the essence of something" is from 1540s; that of "necessary" is from 1520s. Essentials "indispensable elements" is from early 16c. Related: Essentially.
word-forming element making nouns implying a practice, system, doctrine, etc., from French -isme or directly from Latin -isma, -ismus (source also of Italian, Spanish -ismo, Dutch, German -ismus), from Greek -ismos, noun ending signifying the practice or teaching of a thing, from the stem of verbs in -izein, a verb-forming element denoting the doing of the noun or adjective to which it is attached. For distinction of use, see -ity. The related Greek suffix -isma(t)- affects some forms.
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Harper, D. (n.d.). Etymology of essentialism. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/essentialism