짓이기다

Etymology
+ . Equivalent to.

The modern reflexes of 즛 and 니기다 are and  respectively, leading to the modern orthography. However, speakers have actually perceived the verb as a single unit and not a compound, and thus retained the original pronunciation with. This explains the disconnect between the orthography and pronunciation (otherwise very unusual in Modern Korean orthography for verbs, but has the same process).

Verb

 * 1) to crush, to trample