In Mandarin Chinese, reduplication is a very common feature. Its function is to create an informal, less direct or more cute version of a word with the same meaning. For example, 謝謝 xièxie, “thanks”, is a reduplicated 謝 xiè. However, when it comes to naming your relations, it could well be that these apparently reduplicated words came first and then got shortened, just like English “ma” and “pa” are short versions of “mama” and “papa”.
Now mama, papa, baba, dada etc. are babble words, something that babies all over the world tend to produce without thinking about their parents and other relatives. (How on earth Finns got to use äiti and isä, is anyone’s guess. Here’s my own guess: Finnish is derived from Elvish, not the other way round, and elvish babies never babble.) What I find interesting about Mandarin is that there are different babble words for different kinds of brothers, sisters, uncles and grandparents. Which is logical, if you think of it. For example, an older brother and a younger brother often have nothing in common. Calling them simply “brothers” is just silly.
|trad.||爸爸||bàba||dad, papa||From 爸 “dad” formed by reduplication|
|trad.||媽媽||māma||mom, mum, mama||From 媽 “mum”|
|trad.||哥哥||gēge||older brother||From 哥 “elder brother”|
|trad.||弟弟||dìdi||younger brother||From 弟 “younger brother”|
|trad.||姐姐||jiějie||older sister||From 姐 “elder sister, young lady”|
|trad.||妹妹||mèimei||younger sister||From 妹 “younger sister”|
|trad.||舅舅||jiùjiu||mother’s brother, uncle||From 舅 “mother’s brother, uncle”|
|trad.||叔叔||shūshu||father’s younger brother, uncle||From 叔 “father’s younger brother, uncle”|
|trad.||奶奶||nǎinai||paternal grandmother, gramma, granny||From 奶 “milk; woman’s breasts”|
|trad.||爺爺||yéye||father’s father, paternal grandfather, granddad||From 爺 “father, grandfather”|
|trad.||寶寶||bǎobǎo||baby||From 寶 “treasure, precious”|