Backformation from the verb אַרײַנפֿירן (araynfirn, “to introduce”), from אַרײַן (arayn) + פֿירן (firn); at least in part, a loan translation of German einführen (“to introduce”), itself of Latin introducere.
אַרײַנפֿיר • (araynfir) m, plural אַרײַנפֿירן (araynfirn)