The domesticated rambutan is scientifically known as Nephelium lappaceum and belongs to the family Sapindaceae (to which lychee also belongs). There are many wild relatives of rambutan in Sarawak and
Sibu is named after the wild rambutan called Sibau (Iban). The Malays refers to it as Sibo. Very old colonial map has Sibu spelt as 'Siboe". How it later appeared as Sibu on the map is anybody's guess but it could be a mispronounciation or more likely Sibu is the English spelling which is meant to be pronounced as 'Sibo'. (Many words in Iban and Bahasa Malaysia that end with "au" end with an "o" in the Sarawak Malay dialect eg bakau is bako, pulau is pulo, limau is limo and so forth.) It is interesting to note that older generation of Hokkiens and Malays still refer to Sibu as Sibo.
It is possible that Sibau was once abundant in and around Sibu town, particularly on the often inundated bank of the
Rambutan or "the hairy fruit"
Ever wonder why the fleshy part of the rambutan fruit is difficult to detached from the seed unlike longan even though both belong to the same family? The reason is because the fleshy part of rambutan is developed from or is part of the seed coat (testa) unlike the fleshy part of lychee which is not derived from the seed coat. So, the fleshy part of rambutan is also known as “sarcotesta”. Even in the best rambutan variety whereby the flesh part detached off from the fruit much more easily, the seed coat is still attached to fleshy part.
The seeds of rambutan is said to be rich in solid fat which can be used to make soap and candle but is not popular as it is not commercially viable. Rambutan can also be made into jam but has not been popular.
'Pulasan' or Nephelium rambutan-ake
There is another species of rambutan which is hardly hairy at all: Nephelium maingayi. Its Iban name is 'mujau' and the melanau called it 'serait'.