Speculation
late 16th century: from Latin speculat- ‘observed from a vantage point’, from the verb speculari, from specula ‘watchtower’, from specere ‘to look’.
wiktionary
From Middle English speculacioun, speculation, from Old French speculation (compare French spéculation), from Late Latin speculātiō, speculātiōnem, from Latin speculor. Morphologically speculate + -ion
etymonline
speculation (n.)
late 14c., "intelligent contemplation, consideration; act of looking," from Old French speculacion "close observation, rapt attention," and directly from Late Latin speculationem (nominative speculatio) "contemplation, observation," noun of action from Latin speculatus, past participle of speculari "observe," from specere "to look at, view" (from PIE root *spek- "to observe").
Meaning "pursuit of the truth by means of thinking" is from mid-15c. 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.
