This is the 1776th most frequent Russian word.
знал
"Знал" - "knew" (past tense of "know").
This usage of 'знал' indicates past personal acquaintance or familiarity with someone over a period of time.
Я знал его с детства.
I knew him since childhood.
In this case, 'знал' is used in a hypothetical or rhetorical context to express uncertainty about past events.
Кто бы знал, что это случится?
Who would have known that this would happen?
Here, 'знал' demonstrates understanding or knowledge of a particular method or way to achieve something in the past.