TIL that the term "myriad" originally referred to a unit of 10000 and came from ancient Greek origins.
A myriad is technically the number ten thousand
Though in common contemporary English usage it's not referring to an exact number but rather some arbitrary large amount.
This got me looking more into some numbering systems.
There's western based systems that group into units of 1000. So you have things like thousand, million, billion, etc which are all groupings of 1000.
But then you have other cultures that have groupings based on groups of 10000. I remember in Chinese asking for 10000 with 萬 for which the hardest part was not the pronunciation or the vocabulary but the use of units of 10000!