The word "passed" is the past tense of the verb pass which means you just go by something but may not see or check it carecully. be passed (by)-- that is a passive uasage which can be used in the situations where someone is running faster or doing better than the other one. The word "past" is an adjective describing the things that are not present. Sth is past.=Sth is gone. I think it might show a feeling that we'd better not talk about it like what George did to calm down Kramer and Slippery Pete.

That's amazing~