When my sister D was in UCC, in the fifties, one of her French professors was a bit of an amateur etymologist and used to provide light relief during lectures on Claudel by telling them the origins of some words.
I remember her coming home with the story that sincere was from the Latin Sine Cero; without wax, and derived from the sculpture trade when unscrupulous stone masons would repair accidental nicks in their marble with wax, but later, when the sun shone, all would be revealed.
Those scrupulous masons who never used wax were therefore deemed sincere.
It’s a great story but most likely totally invented.
Another word given origin by Le Prof was Marmalade.
Her charming story, which also explained the scottish connection, was that when Mary Queen of Scots was feeling ill nothing would do her but a Confiture of Seville Oranges, by association this then acquired the name Marie Malade, or Sick Mary.
It’s a great story but total rubbish.
Marmalada is a Portuguese Quince Jelly, made from the Marmello or Quince.
It was then stretched to mean any cooked fruit, the French still call stewed apple Marmalade des Pommes.
How the Scottish connection happened I am really not sure, there is a good story of a Spanish ship laden with Seville oranges getting wrecked off the Scottish coast there leading to a glut of Marmalade making from which the scots never recovered.

Seville Oranges make a fleeting visit to Ireland in January and Februry and they make the best Marmalade, they are sharp and really not suitable for much else, except, of course, making an incomparable Canard Sauce Bigarade.

There follows my recipe for Seville Orange Marmalade.
Note this uses Sureset sugar, which I happily use. Should you wish to make it with ordinary sugar you will have to boil it for much longer and test for setting in the usual way.
(Advice not followed by a reporter from the Irish Times last year who used my recipe, but not Sureset sugar, and then complained , in print, because it didn’t set.)

Seville Orange Marmalade

1.5kg (3 lbs) Seville Oranges
3 litres Water
3 kgs. Sureset Sugar.

Put the whole Oranges into a large pot with the water and simmer together for about 90 mts.or until the skin is tender .
Take the oranges out of the water with a slotted spoon and cool, leave the water in the pot.
When they cool halve the oranges and remove the pips. Either discard these or put them in a little square of muslin tied at the edges to boil with the marmalade.
Now cut the halves of orange as finely or thickly as you like.
(If you don’t care too much about the appearance you can chop them up roughly in batches in a food processor)
Put these back into the orange water and add in the sureset sugar.
Bring gradually back to the boil (with the little bag of pips if you are using them) stirring to dissolve the sugar.Let it boil well for 5 mts. test for setting on a cool saucer.It should take no longer than 10 mts. boiling altogether.
Take out and discard the bag of pips, and pot in the usual way.
If you like the flavour of ginger with orange (and I do) you can add two peeled thumbs of root ginger to the oranges as they boil and then chop these finely with the peel and add to the marmalade.