It is kind of like how modern art doesn't mean modern today. It means that time period where people called art "modern". Novel meant new as in "novel science results". It was used differentiate prose (the new style at the time) from epic poetry back in the 16 hundreds and stuck. How that translates to Russian IDK.

I don't speak Russian, but whatever the Russian word is for "book." Or maybe others called it a novel but Tolstoy rejected the label. I'm not sure.

Either way, the word "novel" wasn't necessarily equivalent to how it is used today: any book length work of narrative fiction.

Though watch out, this is a rabbit hole. Just look up novel on wikipedia. You'll see a big orange message at the top which is the first sign there is a problem. And then the article is excessively long. A lot of ink has been spilled trying to define what a "novel" is.