balusteryoudaoicibaDictYouDict[baluster 词源字典]
baluster: [17] Etymologically, baluster and banister are the same word. Both come ultimately from Greek balāustion ‘pomegranate flower’, which reached English via Latin balaustium, Italian balaustro, and French balustre. The reason for the application of the term to the uprights supporting a staircase handrail is that the lower part of a pomegranate flower has a double curve, inwards at the top and then bulging outwards at the bottom, similar to the design of some early balusters.

A balustrade [17], from Italian balaustrata via French, is a row of balusters. Already by the mid 17th century a transformation of the l to an n had taken place, producing the parallel banister.
=> balustrade, banister[baluster etymology, baluster origin, 英语词源]
baluster (n.)youdaoicibaDictYouDict
"support for a railing," c. 1600, from French balustre, from Italian balaustro "pillar," from balausta "flower of the wild pomegranate," from Greek balaustion (perhaps of Semitic origin; compare Aramaic balatz "flower of the wild pomegranate"). Staircase uprights had lyre-like double curves, like the calyx tube of the pomegranate flower.