An Etymological Dictionary of the German Language/Mönch
Mönch, m., ‘monk, friar,’ from the equiv. MidHG. münch, münech, OHG. munih (hh), m. From the prim. form muniko-, monico-, the equiv. Fr. moine is also derived. In the original Lat. word monachus (μοναχός), ‘monk,’ the ch was probably pronounced as c; comp. Ital. monaco, OIr. manach, AS. munuc, E. monk; so that OHG. ch is the HG. permutation of k. In that case Mönch was borrowed at an earlier period than Abt and Pabst (see Münster). OSlov. mŭnichŭ is a G. loanword.