whistle past the graveyard

blast from the past

Something or someone that a person has not seen for a long time that evokes nostalgic feelings.

blow the whistle

To disclose information to the public or to appropriate authorities concerning the illegal or socially harmful actions of a person or group, especially a corporation or government agency.

clean as a whistle

Very clean.

ghost from one's past

Something unpleasant from one's past that "haunts" them (makes them feel uneasy) to the present day.

live in the past

To dwell on and ruminate about past events.

not worth a whistle

Worthless or pointless.

pea-time is past

Something is ruined or gone beyond recall.

put it past

To consider it not possible for (someone) (to do something).