Under the heading of "Things I Think I Used to Know but Clearly Have Forgotten Despite Their Status as Occasional Curiosities," please include an entry on the definition of Mayday. On the one hand, "May Day" is May 1, which is not so much a big holiday Stateside or anything, but enough of one that most people are familiar with it. On the other hand, "Mayday" is an international distress call, whose etymology is most likely unrelated to a holiday celebrating the arrival of spring.
Enter Wikipedia:
Mayday is an emergency code word used internationally as a distress signal. Some people say that it was derived from the French Venez m'aider (help me)...Many official sources, however, say that the word was made up -- like the distress signal SOS -- because it could not be mixed up with any other word, is easy to remember and can be understood even if the strength of the radio signal is weak.
Sure it was made up. It's so substantially different, after all, from words like "payday" and "melee." I realize that it's not currently vogue fashionable 'round these parts to admit to borrowing words from the French Freedom, but puh-lease.
Anyhow, next year, on May 1st, all I'll have to do is to include a link to this entry.