duenna
A chaperon of a young lady, usually an older woman.
'Madam, I have a secret to tell you.' Now the very word secret is enough to rouse any one's curiosity; and, giving a quick glance round to see if her duennas were on the alert, she prepared to listen, and I saw that her eye had caught sight of the letter.
A governess or nanny.
Where it comes from
From Old Spanish duenna or dueña, from Vulgar Latin donna, from Latin domina (“Lady”). Doublet of dame.
Adapted from the Wiktionary entry duenna (CC BY-SA 4.0).