Continuity mistake: In the beginning, Carly gets a bowl and fills it with popcorn up to about 2/3 full. The camera cuts to Sam, then back to Carly, and the bowl is barely full. The camera goes back to Sam then to Carly again, and the bowl is 2/3 full again. Freddie walks in, and the bowl is barely full again, which Carly now fills with popcorn.
Continuity mistake: When the gang is at their apartment watching the news over how they think Carly pushed Shelby's grandmother down, there is a ladder outside their door that appears and disappears from shot to shot.
Answer: In direction translation it means 'Mischievous Spirit'. 'Hob' as in HobGoblin means clown or prankster, and 'Knocker' was an old age term for Poltergeists in mines. Miners would often complain of hearing knocking sounds down mines when there was no-one else down there, hence 'Knocker'. It's not a regular English expression though.
GalahadFairlight