Essential

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Middle English (in the sense ‘in the highest degree’): from late Latin essentialis, from Latin essentia (see essence).

wiktionary

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From Late Latin essentiālis, from Latin essentia(“being, essence”).

etymonline

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essential (adj.)

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.