This phrase means "Cheer up" or "Don't worry, stay happy!" but I understand that it can cause howls of laughter in certain circles, I can't think why!
The pecker in question is probably not a penis, I think it may come from Woody Woodpecker? Or possibly pecker meaning your beak so equating to looking up?
Aarron blushed when his ancientrelative exhorted him to "Keep his pecker up!". He didn't realise that she only wanted him to smile.
Gentle UD editor,as you edit those endless emos and chavs, keep your pecker up!
Trump allies and supporters who continue to stay loyal, kissing Donald Trump's ass by supporting his disastrous authoritarian mentality and Administration for seemingly NO valid reasons.
"I tell'ya Tom... I can't figure out after everything that's transpired, why there are any tRUMPster-Pucker-Uppers still supporting him... it's daunting?"