to get something backwards, understand it backwards (see Molina; who gives this in the first person singular); to guess the secret intention of someone or their dishonest idea (see Siméon)
a hoe Leslie S. Offutt, "Levels of Acculturation in Northeastern New Spain; San Esteban Testaments of the Seventeenth and Eighteenth Centuries," Estudios de cultura náhuatl 22 (1992), 409–443, see page 434–435.