From what I have gathered its another WT translation of the much nicer word "grace"
eg if you were to give your child a gift and then said it was "underserved" how do you think hed FEEL!!
but if you said it was given by grace, it sound loving from the giver and to the recipient
I cant imagine Jesus saying I am the way of everlasting life, (but by the way you dont deserve it)
Just my thoughts
I can find it listed in the gospels!!!!!!!!