It's a shame he didn't choose a female as his human morph because then the Animorphs could call him by the last three syllables of his name instead of the first syllable. Then we'd have 3 males and 3 females in the team whenever they were all human. Jake, Marco, Tobias, Rachel, Cassie and Emily.
Now that you mention it, it does sound sorta like Emily. But Ax didn't exactly choose I guess. I think the morph just ended up male. But if he's female in human morph, then there's like gender switch and I guess it can get sorta confusing
I always thought his resemblance to the name "Emily" was a joke that could have been used in the series. I mean, after all, it's not like he knows the difference between male and female human names, and maybe he likes his name longer since Andalites naturally have names that are three thousand syllables long.
Although I do think he chose to be male, let me pull out book 4:
""I chose to be-be-be-be-be male." He stopped suddenly, his eyes wide."
I give kudos to KA and the other writers being consistent with Ax's character playing with mouth sounds. I think I'd be ridiculously annoyed trying to keep that in for the whole series.