We have Jean-Claude Grouteau to thank for the detail on how the gender of French nouns are decided and remembered by French people. Here is the complete narrative. Merci Jean-Claude:-
When one learns the French language, one has to learn if a word is masculine with le or un, or feminine with la or une. As you have been taught, there is no rule, you just have to learn it. We say la lune (the moon) and le soleil (the sun) Why? In the German language, the moon is masculine (der Mond) and feminine is the sun (die Sonne). Why? An easy way to remember it, is just to think of the Charles Trenet’s song about a date between the moon and the sun. “Le soleil a rendez-vous avec la lune “. … A very good friend of mine learned a lot of the English language by learning song lyrics…
What happens for the French native when a new word appears? There is a common feeling which cannot be explained. So every French person will know at once if it is masculine or feminine and it normally works ….. but not all the time.
So, last year, when the word COVID became a common French word, everybody in France, from the man next door to the medical world, the politicians or the journalists, talked about le COVID. In French speaking Canada, they said, from the beginning La COVID and they were right.
The Académie Française, which is an assembly of 40 wise persons most of whom are famous writers, rules the French language and its evolution. Most of the time, the opinion of the Academy is given a long time after a new word is launched and sometimes this word is then out of use.
But COVID is not really a new word and a rule exists. COVID is an acronym which means Corona Virus Disease. The gender must then be the same as the name, i.e. disease, which means la maladie. So COVID must be feminine. And when speaking French, one should say La COVID dix-neuf.
For this reason, French people say la SNCF (la Compagnie des Chemins de Fer Français, or French National Railways) or la CIA (la Say E A) for une agence is feminine, but le FBI (le F Bee Hi with the letters pronounced as in English) for un bureau is masculine.
But there is another rule which says that the popular use is the right use. Politicians, journalists or scientists are now using La COVID more, but it can be heard or read very often as du COVID (du = de + le) instead of de la COVID.
The French word used for lockdown is confinement. According to my dictionary, in the English language, this word could mean the same as in French but has also other meanings: to be sent to prison or to have a baby. So do not worry if you read in a French newspaper “une vieille dame doit être mise en confinement”. She did nothing to deserve to go to jail or she will not have a baby soon. She just has to Stay at Home Now.