/ ˌgɔːdiən ˈnɒt; NAmE ˌgɔːrdiən ˈnɑːt/ noun
a very difficult or impossible task or problem :
to cut / untie the Gordian knot (= to solve a problem by taking action)
ORIGIN: From the legend in which King Gordius tied a very complicated knot and said that whoever undid it would become the ruler of Asia. Alexander the Great cut through the knot with his sword.
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WORD ORIGIN
mid 16th cent.: from the legend that Gordius , king of Gordium, tied an intricate knot and prophesied that whoever untied it would become the ruler of Asia. It was cut through with a sword by Alexander the Great.