kappa

The word 'kappa' entered English in the 15th century as a direct borrowing from the Greek letter name 'κάππα' (kappa). The Greek letter itself is derived from the Phoenician letter 'kaph', meaning 'palm of the hand', due to the pictographic origin of the symbol. In English, it functions solely as the name for the specific Greek character. Its specialized statistical meaning, 'Cohen's kappa', was coined in the 20th century by the psychologist Jacob Cohen, who repurposed the Greek letter as a convenient algebraic symbol for his new measure of inter-rater reliability, thereby extending the word's semantic field from linguistics to mathematics.

This is a simplex loanword from Greek. The word 'kappa' itself is the name of the letter and does not contain separable, meaningful morphemes within the context of the English language.