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Sounds like, "shi shi" right? That means, "urine" in Hawaii.

Haha not quite... the tonality of it is very important, so depending on the pronunciation it could mean "write", "shoes", or "rest a while"

The compound word 鞋鞋 xiěxié / shiieeshye is a word used by infants or their mothers speaking “motherese”: “shoesies”: 你的鞋子在哪裡啊 Nǐ de xiěxié zài nǎlǐ a / Niid shieeshye tzay naalii a? “Where are your shoesies?”

The other duplicated words are less common and not worth noticing.