Why is it called the monkey jump?
Apparently the shape of the monkey jump is reminiscent of the crape myrtle tree. The Japanese name for crape myrtle is sarusuberi, written in kanji as 百日紅. However, sarusuberi can also be written with the characters 猿滑り, where 猿 (saru) means "monkey" and 滑り (suberi) means slide--hence "monkey jump". The characters for the go term (see CJK box on the main page) are not the ones for the tree.
BuggyMind: So "monkey slide" is a better translation, as well as being more appropriate because it's a slide?
According to the Wikipedia page linked above, 百日紅 is ateji; the name sarusuberi, meaning "monkey slip", refers to the smooth, slippery bark.
 As far as I can quickly tell from looking things up, it's jukujikun (kanji chosen for meaning, not pronunciation) for "hundred days red", and there's no way to actually get the pronunciation "sarusuberi" from it.