It would not be uncommon for me to use Autumn or Fall, but I probably say Autumn more often than not. This is because I have a friend who will make a stupid joke about falling or some other stupidity and that got old many many years ago.
That makes sense. Thanks! 
Here’s a link to the actual pronunciation. “OH-seen” is not a bad approximation of it, although something like “OH-s(y)in(y)” (where “(y)” indicates palatalization) would be more accurate. Russian orthography is not completely phonetic. An “e” in an unstressed position becomes a short-i type of sound. You can read about Russian vowel reduction here.
I’d heard the same thing, and was planning on posting just that.
Origins of the specious: myths and misconceptions of the English language by Patricia T. O’Connor has this to say about the origins of ‘fall’ and ‘autumn’:
So “fall” is a legitimate English word fossiled in the Americas, much like “apartment” or “gotten” (both often mistaken for Americanisms, both, like “fall”, English words largely abandoned by their country of origin).
I use 'em pretty much interchangeably. Not much rhyme or reason to it, other than maybe the number of syllables.
“Vacation” is an Amercanism? What do they call it in Australia, then? 
Everybody goes on “holiday.”
I mostly (but not always) say “fall”.
Greek: φθινόπωρο (fthinoporo), which roughly translates as “fall of the fruits”.
Fall: short, blunt, casual, American, to the point (like me!)
Autumn: more … poetic, a bit high-falutin’, more descriptive of the season than the actual event. Martha Stewart can expound on her new collection of washcloths in autumnal colors. But kids go back to school in the fall, not autumn.
I think “autumn” sounds nicer than “fall,” though I use both equally as often. Whichever I feel like saying I say.
秋天 (qiu tian) in Chinese
On the footpaths, no doubt.
Right now in Houston, I’m calling it “Sweet Baby Jesus, will it never be cooler in the daytime than “feels like” 105? Please come to me, sweet cooling winds!”
Though, usually, I use fall or autumn interchangeably.
Autumn except for when I’m in the tropics in which case winter becomes “The Dry”, spring becomes “The Build Up”, summer becomes “The Wet”, and autumn becomes nothing in particular.