Yeah immigration and mix of similar names from different languages could also be reasons for the (at least perceived) shifts.

This is part of what they mean by girl names driving the shift. You have a traditional ethnic name that may be masculine or feminine and has a baseline low level of popularity. Then you have a popular female name that rapidly gains and loses its popularity. The effect on the mix is that it's shifting from masculine to feminine, but really you should look at it as a newly-popular female name being layered on top of the traditional name. And you can often see this in the timescale, with a clear pop-culture trigger leading to the rising girl name.

Looking at just part of the data, I can see this with Arya (Stark, Game of Thrones), Paris (Hilton), Stevie (Nicks, of Fleetwood Mac), Dakota (Fanning), and Tatum (O'neal), and the masculine trend also relates to the fading of generationally-popular names like Jean (Silent/Boomer), Pat (Boomer), Joan (Silent/Boomer), Courtney (Gen-X/Xennial), etc.

Don't forget Madison[1] (Splash[2]). My guess is that the majority of names prior to 1984 are clerical errors where the surname was entered as the given name.

1: https://namedaisy.com/us/name/Madison

2: https://en.wikipedia.org/wiki/Splash_(film)

I was actually surprised to see Trinity in the list. Not only does it remind me of The Matrix (1999), I also don't think I've ever encountered someone with that as a real name.

Kim is another good one - I've met several Korean men named Kim.

Though I'm not 100% sure they weren't using their family name as their everyday identity name (the Kims I met were not related).

Australia: Kim was a common male name

Kim is also a shortened form of Joachim.

Kim actually is usually a family name, but it's written first.

Kim Jong Un, right :)

Very likely it's their family name. Kim is the most common family name in Korea. Most Korean given names are two characters (=2 syllables) and more difficult to pronounce and memorize for westerners. And because of the space inserted between two romanized syllables (Jong Un), they are often misunderstood as middle + given names.

The current Kim's dad didn't help here giving his son a name that's so similar to his own.

In Britain we had the very famous MI6 Intelligence office Kim Philby who was also a Russian spy, he was a key part of the Cambridge Five spy ring.

What I didn't know until just now is Kim was just a nickname. He was Harold Adrian Russell Philby and apparently Nicknamed "Kim" after the boy-spy in Rudyard Kipling's novel Kim[2] which surely foreshadowed his career!!

[1] https://www.bbc.co.uk/news/uk-24803131

[2] https://en.wikipedia.org/wiki/Kim_Philby

Kim is the name of the protagonist of one of the most popular boys' novels of all time, and there are a number of examples of well known male Kims from the twentieth century.

I was going to say the same about Jean; I think that one at least is hard to really draw conclusions from without additional data like languages spoken at home.

Anecdotally, the boy->girl names are almost all very popular names where I've met multiple each of those across different ages, whereas the other two categories feel like they have a lot more down-list entries.

Gender change with the same pronunciation would be a difficult to compile but interesting refinement.

Going by the peak time on the chart, Jean flipped over fast right about when Jean-Luc entered public consciousness.

I think that's an example of what he's talking about. Jean-Luc is pronounced "John Luke" whereas the feminine form is Gene. And similarly the male Jan is pronounced Yan.

[delayed]

I am not a native English or French speaker but the way I've heard Luke being said in UK/US English and the way I have heard the filmmaker's name pronounced that Luc doesn't really sound like Luke. I feel the u and c are shorter and subdued.

Yeah Jean is pronounced more like 'Jawn' but I just mean it's a clearly male name in either case, as opposed to Jean pronounced 'Gene' which is generally a female name, though oddly 'Gene' also pronounced the same is generally a male name.

Probably more in the US. In the UK John and Jean (with a french pronunciation) sound completely different. John has a hard O sound, and Jean has a soft J and an elongated aw sound

I knew a Jan who was actually named January, and she was the only one I've ever met with that name.