“See, this day I set before you blessing and curse: blessing, if you obey the commandments of the LORD your God that I enjoin upon you this day; and curse, if you do not obey the commandments of the LORD your God, but turn away from the path that I enjoin upon you this day and follow other gods, whom you have not experienced [asher lo-y’datem].”
—Devarim/Deuteronomy 11:26-28 (trans. from JPS/Plaut
Throughout Devarim/Deuteronomy, Moses has reminded the people, in essence, “you were there”: You saw. You heard. You covenanted. Etc. This portion introduces an additional idea: You “knew/experienced/[yod-dalet-shem]” God.
Alter translates asher lo-y’datem as “which you did not know”; Fox “whom you have not known.” (The verb, y’datem, by the way, uses the second-person masculine plural, which can address a male group or an inclusive one.) The Torah: A Modern Commentary includes a note on the verb:
Experienced. The word [yod-dalet-ayin] describes sometimes intellectual apprehension and at other times an intimate, living relationship; see Hosea 13:4 and, in sexual respects, Gen. 4:1 (and our commentary to Gen. 2:25-3:24, “Sexual Interpretation”).
Only I the LORD have been your God
Ever since the land of Egypt;
You have never known a [true] God but Me,
You have never had a helper other than Me.
— JPS translation; the verb, teida, is second-person masculine singular, addressing “Ephraim”
The comments on “sexual interpretation” referenced above note that the verb [yod-dalet-shin] “has the meaning of experience, especially of sexual experience. Note that the story of expulsion from Eden begins with a discovery of nakedness and sexual shame (Gen. 3:7).” The commentary goes on to explain that eating from the Tree of Life would have bestowed earthly immortality; instead, having tasted of the Tree of (Sexual) Knowledge:
Man must now perpetuate his species through procreation, in the same way as other creatures do. But being a man, his sexuality has a special dimension; his process of passing from childhood to adulthood, from innocence to maturity, is shot through with love and pain…As a child he lives in a garden of innocence; when he discovers his sexual impulse and grows up, he must leave the garden forever. — comments on “The Tree of Knowledge” from The Torah: A Modern Commentary, as noted above
Full citations and links for translations and commentaries referenced here can be found in Source Materials.