The implication is that Musselburgh was a town (Burgh is derived from the old english word for town) before Edinburgh and will still be there long after Edinburgh is gone. Of course this is debatable as Musselburgh's earliest inhabitants arrive around 80AD after the Roman invasion of Britain whereas Edinburgh already had a tribe of peoples known as the Votadini living in the area, although wether they actually had settled within the bounds of modern Edinburgh is unclear.