The negative report given by the people who are sent to scout the land of Cana'an before Bnei Yisrael go in, resulting in the punishment that they have to wander for another 38 years in the desert, is commonly referred to as the "cheit hameraglim". In the Torah, however, these people are referred to using the root תור when given their mission in Bamidbar, with חפר also used when recounting their mission in Devarim. The only time the root רגל even appears at all is in one mention by Moshe in Devarim 1:24Devarim 1:24 when he tells the next generation about what their parents did in the land, yet this root is the one commonly used when talking about it today (i.e. "cheit hameraglim" and not "cheit haturim" as one might expect).
What is the first recorded use of this phrase to refer to the event?