This is the 8204th most frequent Russian word.
мо
"Мо" is not a standalone word in Russian; it may be a typo or part of another word.
In this hypothetical use, 'мо' would signify possession, though usage directly here in this way is unconventional in Russian.
Я слышал это мо вчера.
I heard it yesterday of mine.
Here, 'мо' represents a possessive pronoun for 'property', signifying ownership.
Мо имущество находится в безопасном месте.
My property is in a safe place.
'Мо' here is part of 'мо удивлению', conveying ownership in an emotional context — my surprise.