Linguists use the term reduplication for words that partly (or entirely) repeat themselves—for instance, tick-tock or ding-dong. (Does it strike you that the re- is a little redundant and they could just be called duplicated?)
Names for girls and women often have this pattern: Dede, Lulu, Mimi.
And so are some of the first words we learn: Mama and Papa. Children get booboos, and bathroom words often have the pattern too. Words we use all the time have it: bye-bye, ta-ta. The Rolling Stones wanted us to get our ya-yas out (that is, to be uninhibited) and even get into La-La land. We might want to do the can-can or the cha-cha, and, if we do, maybe we’d like it done on the hush-hush.
Some people poo-poo reduplications as a word-making strategy in English, even though they acknowledge their importance in languages of the Pacific where we get some borrowed words: laulau, mahi mahi, and poipoi, for instance. (Google these words yourself to see what tasty foods they are.)
There’s something wonderfully childish about a lot of them: choo choo, puff puff, toot toot.
Off we go.