'speculate' originates from Latin, specifically the word 'speculatus,' where 'specula' meant 'watchtower' or 'lookout.'

'speculatus' transformed into the Medieval Latin word 'speculatus,' and eventually became the modern English word 'speculate' through Middle English.

Initially, it meant 'to observe from a high place,' but over time it evolved into its current meaning of 'to form a theory or conjecture.'