'theorist' originates from the Greek word 'theōristēs,' where 'theōria' meant 'contemplation or speculation.'

'theōristēs' transformed into the Latin word 'theorista,' and eventually became the modern English word 'theorist' through Middle English.

Initially, it meant 'one who contemplates or speculates,' but over time it evolved into its current meaning of 'a person who develops ideas and principles.'