def produce_paired_etyma(roots1, roots2):
  """Produce a paired list of etyma.

  Args:
    roots1: A Roots class instance
    roots2: A Roots class instance
  Returns:
    zipped list of pairs of etyma
  """
  roots1_etyma = roots1.produce_etyma()
  roots2_etyma = roots2.produce_etyma()
  assert(len(roots1_etyma) == len(roots2_etyma))
  return zip(roots1_etyma, roots2_etyma)