Once upon a time, something happened to boys’ names ending in the letter A. Or rather, two somethings. Starting around 1970 the typically female -a ending was twice transformed, and the sound of American boys hasn’t been the same since.

See for yourself. The top black line in this chart represents the number of boys receiving -a names from 1900 to today.

As you see, -a names were rare but steady until they…shall we say fell up a cliff? But it’s not just a simple before and after story. First off, even the low base level of -a boys in the early years of the chart is artificially high. Data errors are common in name stats from that period, and a significant percentage of the names listed as -a boys look like probable coding errors. For instance, the girls’ names Anna and Bertha show up among the top 500 boys’ names of 1900.

More importantly, the big monolith from 1970-2019 comprises two very different trend eras. I’ve shaded the chart to reveal that the initial stark leap is, quite simply, Joshua. In the course of just a few years, that one -a name quickly rose to eclipse all others.

Then, in the past generation, the picture shifted again. Joshua has now retreated to its lowest popularity point in almost half a century, yet -a boys overall are soaring once more. Ezra and Luca have joined Joshua as top-100 favorites, and 15 other -a names rank in the top 1000. For the first time, the U.S. has a real culture of boys’ names ending in -a.

This change becomes even more evident when you broaden the view from the letter a to the sound a. Take a look at what has happened to boys’ names ending in -ah, like Noah and Elijah:

For perspective, the -ah ending now dwarfs the popularity of masculine standbys like -d names, as in David, Richard and Edward, and -k names, as in Jack, Patrick and Mark. It signals a transformation of the sound of American boys—and soon, of American men.

It’s tempting to attribute the shift to changing attitudes toward gender. Perhaps parents of boys today are more open to styles that past generations considered “feminine.” The -a names being chosen for boys, though, are overwhelmingly traditional male names, not gender crossovers. What’s more, girls ending in -a still outnumber boys by more than 20:1.

The motivation for the -a rise is more likely to be simple fashion: this is a vowel-dominated style era. But the effect of the rise may be another story. The names we grow up hearing are part of our cultural perspective. For this generation, male and female names that sound a little less separate could be one more subtle factor eroding expectations of a rigid gender dichotomy.