Possibly from an earlier expression j.nḏ.jḥr, meaning roughly ‘may I inquire about (you)’, with nḏ in the subjunctive and the first-person suffix pronoun .j omitted.
James P[eter] Allen (2010) Middle Egyptian: An Introduction to the Language and Culture of Hieroglyphs, 2nd edition, Cambridge: Cambridge University Press, →ISBN, page 199.