What is なんでって a contraction of in this sentence?

Question

今じーちゃんとこなんでって…
"Right now I'm at grandpa's" (source context)

In this case the speaker is on the phone so his speech is casual and fragmented.

I already have an idea of what the sentence means, what I am hoping to understand is:

• What なんでって is a contraction of?
• And what it is doing in this sentence grammatically? What nuance does it add?

I know that とこ is a contraction of のところ but what is なんでって, is it なので? I know って is often と or sometimes という but that doesn't seem to make sense in this context, at least to me as a beginner.

Answer 1

The actual phone conversation would have gone like this:

Guy: 「あ、おかあさん？オレ。今じーちゃんのとこ。」

Mom: 「なんで（じーちゃんのとこにいるの）？」

Guy: 「なんでって・・　別{べつ}にィ～～～」

What なんでって is a contraction of?

It is of 「なんでと」. This 「って」 is the informal version of the quotative particle 「と」.

「なんでと」 in this context means 「なんでと言{い}われても」or 「なんでと聞{き}かれても」, which would roughly translate to "Why? Because...".

And what it is doing in this sentence grammatically? What nuance does it add?

「と/って」 here introduces the speaker's intention of replying to the question asked by the other person. The question here is of course "Why are you at your grandpa's place?" asked by Mom to which the son replies 「別にィ～～」 ("No reason.")