the wife or widow of an Elector of the Holy Roman Empire
Word origin
[1610–20; elect(o)r + -ess]This word is first recorded in the period 1610–20. Other words that entered Englishat around the same time include: institutional, integration, intonation, objective, system-ess is a suffix forming distinctively feminine nouns. Other words that use the affix-ess include: adventuress, canoness, heiress, preceptress, stewardess