some words it is good to say again after you have said them. you must say a word the correct number of times only, otherwise it sounds wrong and your leg might fall off or something equally bad. the number is often two or four, but it depends on the word. some common words are listed here:
yup yup
good good
yah yah yah yah yah
there are also some exceptions. ‘dooooo’ and ‘laaa’ for instance can be of variable length and thus have varying repetition properties, much like the transition metals.