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late 14c., "contemplation, consideration," from Old French speculation, from Late Latin speculationem (nominative speculatio) "contemplation, observation," from Latin speculatus, past participle of speculari "observe," from specere "to look at, view" (see scope (n.1)). Disparaging sense of "mere conjecture" is recorded from 1570s. Meaning "buying and selling in search of profit from rise and fall of market value" is recorded from 1774; short form spec is attested from 1794.