isnt'nt

equivalent to wasnt'nt. is not not. double negative meaning is

max isnt'nt good at this game

wasnt'nt

equivalent to isnt'nt. was not not. double negative meaning was

i wasnt'nt cheating, i swear

Gerd

Equivalent to neek, NErd+geEK=neek therefore gerd=GEek+neRD. Its often someone who think they do anything and/or doesn't take any advice from others. They go out of their way to work/learn. They often don't know slang.

person 1:"yo Harry come play COD with us when u get back ye, Jake just got the game and he's tryna rank up."
person 2:"sorry, no because my teacher would be very disappointed in me if I do not complete the work she has set"
person 1:" oh my daaaaaze man why you such a gerd lately. "

didnt'nt

equivalent to dont'nt. did not not. its a double negative basically meaning, did. can be often used as a brag/show off.

i didnt'nt win the race in front of the whole school.