The derivation looks more complicated than it really is:
(1) reduplication suggests repeated action;
(2) /ye/ metathesizes with /m/ of the reduplicated prefix; /y/ is elided and /ea/ is realized as /e/;
(3) the /ë/ of /-ënt/ is rounded to /ù/ by the preceding /m/.

See also - mehmalamùntikaon, a variant pronunciation.