https://www.tumblr.com/thisis-misogyny/819934703308111872/the-way-manly-is-a-compliment-but-girly-is-an not trying to say this person is wrong or anything! If this isn’t welcome please just delete this.
I just think a better comparison would be between the words boyish and girly, and the words womanly and manly. As ‘boy’ and ‘girl’ both are younger words than ‘man’ and ‘woman.
I still think there’s something there, of course. Both the words boyish and girly imply immaturity, but the word boyish is used far more positively than girly. Typically, it’s used to mean someone is energetic and lively, sometimes playful. Girly is either often used as an insult to imply that someone is weak or feminine, or to refer to things that are seen as feminine like makeup or fashion.
Womanly and manly both have positive connotations, but I do still think it’s fair to criticize their meanings. The cultural usage of manly is, like the word boyish, is often used positively and has a pretty broad set of ‘manly’ traits associated with it—like courage, strength, and independence. But womanly is narrower, and is used to invoke a very specific, much softer and gentler image. There’s a clear imbalance here.
^^^