The term devoted
(ḥērěm) refers to placing a ban on something. The object is then restricted and should be avoided. In this context, it refers to something that has been promised to the Lord by a solemn vow. The object of this vow is completely and absolutely irredeemable.
28 “But no devoted thing that a man devotes to the LORD, of anything that he has, whether man or beast, or of his inherited field, shall be sold or redeemed; every devoted thing is most holy to the LORD.