ADDED: MY ANSWER BELOW IS COMPLETELY WRONG! Please see my next posting.
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A great question! A great opportunity for me to give a long answer to a short question!
"Faire" isn't French, it's old-fashioned English.
In the United States there have always been some people who enjoyed dressing up or pretending to be historical characters, and acting out history. People dress up as Civil War soldiers and "reenact" famous battles, and so forth. We also enjoy thinking about the days of King Arthur or Robin Hood and the old-fashioned English of the time. Someone might think it was cute to call their restaurant "Ye Olde Village Tea Shoppe," for example.
In the 1970s or so, more and more people started to play role-playing games, dress up as knights or wizards or Klingons, and developed events called Renaissance Faires. These were theme-park-like events, lasting for a few weeks, where people dressed in costumes and staged swordfights and tournaments and things.
In the 1970s the personal computer sprang up. A lot of the early computer pioneers called themselves "hackers." And a lot of them enjoyed fantasy role-playing games and knew about Renaissance Faires. So, early personal computer conventions and meetings were often called "faires." The West Coast Computer Faire was a very important annual event in the late 1970s.
In other words, "hackers" went to "computer faires."
I believe "Maker" is an attempt to modify the word "Hacker" to make it more acceptable to the general public. At any rate, the "Maker" movement, which seeks to empower ordinary people through access to high-tech tools like 3D printers, calls its meetings "Maker Faires." I think they are doing it because they feel they are in the tradition of the West Coast Computer Faire.