It was a floral name which conveniently contained
Mary. The entry says it was used from the 19th century onwards.
If I look at all possible
Dutch equivalent, they first usage (since registration in 1880) is 1920 for
Rosemarie and both Rozemarijn and Rosemarijn weren't used until a little bit later. Since the latter 2 are spelling variants of the actual herb, it would lead me to think that the Marie/Mary/Maria connection was partly what pushed the name forward. But that's me interpreting data. And also because the same thing is also true for my name
Marjolijn /
Marjolein is a herb (marjoram), but it's usage is driven by it's connection to
Maria. In fact my own parents even meant it as a form of
Maria, bc I'm baptised as '
Maria'. It's comparable to the nickname thing in English, except the used form isn't necessarily shorter or more nicknamey.