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The topic or a variant of it is first in print in 1888 or 1867, respectively. But, Genesis 25:26 says, “After this, his brother came out, with his hand grasping Esau’s heel [and, by word picture, pulling Esau’s leg]; so he was named Jacob.” NIV. The NIV also has a footnote, “26 Jacob means he grasps the heel (figuratively, he deceives).”
Ignoring shades of meaning between deceive and fool, it seems perfectly logical to me that while the words are slightly different, the real origin of linking pulling one’s leg and fooling someone is much older than the link above indicates.
Does this cast doubt on the real origin of pulling one’s leg?
Interesting question. Ngrams validates your time frame. The etymology may have its origin in Genesis, but popular use of the metaphor emerges ca. 1900.