interestinterest

Interest comes from Old French interesse, from Medieval Latin interesse, from Latin intersum ‘to be between, concern’, ultimately from Proto-Indo-European *h₁es- ‘to be’.

1. Proto-Indo-Europeanc. 4500–2500 BCE*h₁es-¹‘to be’reconstructed
2. Latinc. 75 BCE–200 CEsum¹‘to be’
3. Latinc. 75 BCE–200 CEintersum¹‘to be between; to concern’
4. Medieval Latinc. 600–1500intersum¹‘to concern’
5. Old Frenchc. 842–1400interesse¹
6. Middle Englishc. 1150–1500interest¹
7. Englishearliest quotation c. 1597interest¹

1. ¹ Wiktionary, English interest
2. Earliest quotation in Wiktionary’s entry: c. 1597, William Shakespeare, The First Part of Henry the Fourth, […]: “You shall have your desires with interest”.