This question has a built–in trap for the unwary setter (or answerer). 'Polyanthus' means 'many flowers', but so does Floribunda, which is a cultivar (type) of rose. The former is from the Greek, while the latter is from the Latin.
'Polyantha' is another cultivar of rose, and this name also, obviously, has the same meaning.
If setting this question, I would suggest there are two ways to avoid falling into the trap (or setting it). You could specify whether you're looking for the name that comes from the Greek or the one that comes from the Latin; or you could allow either answer.
© Haydn Thompson 2019