Continuity mistake: Spencer is talking to the Sunshine girls about stealing his spot. After he gets pushed in the street, when his skateboard goes flying and breaks in two, one half goes offscreen, and one goes under the table. In the next shot both halves are by his feet, but in the next shot they are back in their original positions.
Continuity mistake: When Spencer and Carly are blowing bubbles to the ceiling, when the bubbles pop, and the soap comes down, Carly's hair is all knotted and messed up. But when she sits up, her hair is perfectly parted and straight.
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