Why do we add the letter "D" to.....?

My first reaction was to give you the accepted answer that if we shortened it to "Frig" it would have a very different meaning and would not be pronounced like the syllable in re"frig"erator. The same issue would exist with the meaningless shortening to "frige"

But on research I find that the spelling "refridgerator" is quite commonly used as an alternative spelling, so that "fridge" is then a contraction of that spelling alternative!

NEWA, I'm going to use "refrijerator" and "frij" in future! Just to spike the controversy

just another of the random things in the english language that has no other purpose other than to confuse the foreigners trying to learn the language