Michchhami means to be fruitless (forgiven) and Dukkadam (Dushkrut)
means bad deeds. Therefore the meaning of Michchhami Dukkadam is my bad
deeds (with you) be fruitless. So concept behind saying or writing
someone "Michchhami Dukkadam" is that if I have done any harm to you,
then those bad deeds to be forgiven (be fruitless).
Those who are born in Jain families are familiar with the meaning.