The phrase ‘motley crew’ derives from the eighteenth century. ‘Motley’ is a medieval word meaning mixed in colour and often referred to clothing. The Motley was therefore the court jester due to his multi-coloured costume.
The meaning of the word then developed to mean ‘mixed bag’ or ‘various things’ so the phrase ‘motley crew’ began to be used to mean ‘a roughly-organized assembly of characters’. The first use is found in 1748 in George Anson’s Voyage Round the World:
With this motley crew (all of them except the European Spaniards extremely averse to the voyage) Pizarro set sail from Monte Video.
By the nineteenth century, ‘motley crew’ was an well-used cliché. It refers to a mixed group of unlikely heroes coming together to overcome adversity. It most often referred to pirates and is now a common archetype for sports and science fiction stories.