What is the literal meaning of どういたしまして?

Question

どういたしまして 【どう致しまして · 如何致しまして】

you are welcome;  don't mention it;  not at all;  my pleasure; —Usually written using kana alone.

「手伝ってくれてありがとう」「どういたしまして」 "Thank you for your help." "It's my pleasure."

「ありがとうご座います」「どう致しまして」 "Thank you." "You are welcome".

(致す ita.su = doth;  do;  send;  forward;  cause;  exert;  incur;  engage)

如何 (どう) dou (adverb): how;  in what way;  how about; —Usually written using kana alone.

How do the two words come together to mean, "you're welcome."?

Is it an abbreviation of an older phrase?

Answer 1

This one can be beautifully summarized by a simple quote from wiktionary:

語源[編集]
どう、いたし・まし・て＜「どう（どのように、何を）」+「いたす（「する」の謙譲語）」+「ます（丁寧語を造る助動詞）」+「て（反問的用法の終助詞）」）。
「何を、したというわけでもありませんよ（だから、気になさらないでください）」の意

It's fairly self explanatory, but to give a breakdown in english:

• どう = どのように
• いたす = する in humble language
• ます is the polite verb ending, but in te form, where...
• て is "反問的用法の終助詞," the formal English name for which I don't know. It is basically a final particle used for a returning remark.

The final rough translation (of the example sentence from wiktionary) would then be something like "I didn't really do anything anyway so don't pay it any mind." However as blutorange points out, the negative notion of not having done everything comes from it being a humble polite form of どうして, so it's like asking "what did I do to be worthy of thanks?" or "Why thank me?"