(1) The difficult version of jump rope in which players jump over two ropes that are swung in a crisscross manner by two turners
(2) An incomprehensible talk
WiktionaryText
Etymology
double + Dutch For sense 1:
The English, historically, found Dutch (albeit a fellow Western Germanic language) particularly difficult to understand so anything that was completely incomprehensible would be double Dutch, i.e. twice as hard as Dutch.
