How to type ドゥ (which is a 拗音) or ドゥー? (Windows IME)

Question

Update: The question was partially wrong -- specifically in its assertion that ドゥ is a 拗音 (ようおん). The correct concept should instead be Small Kana. Please see Elrikr Utlendi’s excellent answer below. Later I also found this article on small kana. I've decided to retain this question as is because other Japanese beginners may come to a question like this via a similar mistaken route.

Original Question:

I can type most Japanese on Windows IME, but I am stuck with this one.

How can we type ドゥ or ドゥー?

It is used in this word (meaning "Hindu")

ヒンドゥー

I know ド is do

and ウ is u, but here it is a smaller one meaning a 拗音（ようおん）-- a relatively rare one that is not shown on my text book (みんなの日本語)

Google Translate gave me this Romanji

Hindo~ū

which also looks very odd to me. I could not use this romanji with my Win IME to get the Japanese words

I tried du, Win IME gave me づ

I tried dou, Win IME gave me どう

Answer 1

There are a couple things going on in your post that I'd like to address.

Terminology

You mentioned the term 拗音【ようおん】. As spelled, the word literally means 拗【よう】 ("bend, twist") + 音【おん】 ("sound"), in reference to the way that 拗音【ようおん】 are not "straight" or plain vowel sounds, which are also known as 直音【ちょくおん】 (literally "straight" + "sound"). In phonetics terms, 拗音【ようおん】 are technically known as "glides" or "semivowels".

In the mora //du//, we have no glide, only the plain //u// vowel, so this is not a 拗音【ようおん】.

→ I suspect you were using the term 拗音【ようおん】 to refer to the small kana. These are usually called 捨【す】て仮名【がな】 (literally "throwing away" + "kana"), and sometimes also called 小書【こが】き仮名【がな】 ("small writing" + "kana") or 小書【こが】き文字【もじ】 ("small writing" + "character").

Input

To follow up on Kaskade's comment, when using common Japanese IME software like the ones included in MS Windows or Mac OS, you can input the regular Japanese 捨【す】て仮名【がな】 by typing "l" (that's an L as in "like", not a number 1 and not a capital I as in "igloo") or "x" and then the normal kana sequence. Examples:

• Small う = lu or xu = ぅ
• Small つ = ltu or xtu = っ
• Small ゆ = lyu or xyu = ゅ
• Hindu = hindoxu or hindolu = ひんどぅ

There are also other small kana used to write Ainu, things like small ㇰ (final //k//) or small ㇻ (final //r// after an //a//). I haven't found any way to input the Ainu-specific small kana using the Microsoft Japanese IME in its default setup, but most IMEs are configurable, and it might be possible to add these kana to the IME.

Answer 2

The Windows IME (and I think other OSes too) supports out of the box:

• トゥ: twu
• トゥー: twu-
• ドゥ: dwu
• ドゥー: dwu-

Thus,

• ヒンドゥー: hindwu-