Learn something new every day: decimal and octal i

Apparently, Cyrillic и and і (both pronounced [i] in at least one language) derive from Greek η and ι, respectively (which were also both pronounced [i] at the time the Cyrillic alphabet got started).

And the reason why two characters were kept even though they represent exactly the same sound has to do with the use of letters as numbers: the two letters represent the numbers 8 and 10, respectively (hence "decimal i" and "octal i", as they are, it seems, sometimes called).

Interesting; I never knew that и was descended from η, but it makes sense, not least due to the letter shape.