Vast

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late Middle English: from Latin vastus ‘void, immense’.

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From Middle French vaste, from Latin vastus(“void, immense”).

etymonline

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vast (adj.)

1570s, "being of great extent or size," from French vaste, from Latin vastus "immense, extensive, huge," also "desolate, unoccupied, empty." The two meanings probably originally attached to two separate words, one with a long -a- one with a short -a-, that merged in early Latin (see waste (v.)). Meaning "very great in quantity or number" is from 1630s; that of "very great in degree" is from 1670s. Very popular early 18c. as an intensifier. Related: Vastly; vastness; vasty.