Brewer's: Spun Out
As “the tale was spun out”- that is, prolonged to a disproportionate length. It is a Latin phrase, and the allusion is to the operation of spinning and weaving. Cicero says, “Tenu'o deducta poemata filo ” - that is poems spun out to a fine thread.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894