Thoroughgoing, complete. The term, which dates from at least the sixteenth century, alludes to cloth made from wool that was dyed while raw (before it was spun) instead of being dyed piece by piece. The color therefore was “true” throughout, and this concept was transferred to other kinds of genuineness. “In half an hour he can come out an original democrat, dyed in the wool,” said Daniel Webster in a speech (Feb. 10, 1830). It has been a cliché since the early 1900s.