This probably refers to people who cut their hair short in order to honor a pagan god. Some modern versions interpret this Hebrew expression as "all the people who live on the edge of the wilderness."
The word "nations" refers to the people who live in these places. Foreigners being uncircumcised was a sign that they were not in Yahweh's covenant. Alternate translation: "For the people of these nations did not enter into a covenant with Yahweh through circumcision" (See: [[rc://en/ta/man/jit/figs-metonymy]] and [[rc://en/ta/man/jit/figs-explicit]])
The "heart" represents a person's will and desires. An "uncircumcised heart" represents the character of a person that does not follow Yahweh and his laws. Also, the "house" of Israel refers to the people of Israel. Alternate translation: "all the people of Israel are only circumcised on the outside and have not changed their hearts" (See: [[rc://en/ta/man/jit/figs-metonymy]] and [[rc://en/ta/man/jit/figs-metaphor]])