I don't understand how it is sickly sweet or infantile. It's a normal English word name. It's in the same category as
Lily and
Ruby to me - sweet word names with good meanings and a lovely, sweet sound.
It will definitely suit an adult. Sound-wise it is not much different from
Lily,
Ruby,
Lucy - even
Mary.
I really like it as well. I would spell it
Posy, like the word.
Posie is odd to me. Posey is okay too, then it's not a word name to me anymore but more of a surname-name.
So
Posy is better than
Posie and Posey and Posey is better than
Posie.
I don't really understand why so many people seem to have such a big problem with it, maybe they don't know it's a word name?
To me it is in the
Ruby,
Lily,
Lucy,
Mary category (sound-wise, style-wise only in the
Lily and
Ruby one).
I find it more mature sounding than
Daisy and especially
Poppy.
Please rate my list:
https://www.behindthename.com/pnl/6232