To preface this, I'm going to go over what echolalia is. In simple terms, it's the unintentional repetition of speech, most often of others' speech, though I've seen some folks who repeat their own words (similar to some stutters in a way). It's a typical part of speech development, but tends to drop off as a person grows. Autistic people are more likely to continue experiencing echolalia even as they grow, however.
One bizarre thing we've noticed with our echolalia is that sometimes we end up repeating each other's words, whether we heard/saw ourselves speak them out loud, in writing, or via internal communication. This last one especially was very confusing for a long time, doubly so since we can't always tell who is who (or who's speaking) in our head – the speech felt unintentional, but since we'd thought about what we were going to say before we said it, we assumed we'd intended to say [out loud] whatever it was we did. Nope! Our brain just picked up on our internal speech, called it good enough, and sent the signal to talk before we'd even caught up with the original thought.
While this sometimes works out in our favor, it can also be annoying and embarrassing when we say something out loud that was just meant to be an in-sys conversation or private thought. Or when we end up with echolalia of our written words, it just sounds/looks like muttering on the outside, which can annoy others. People aren't always nice about it, but we've learned to ignore it over time. Now that we've figured this out, though, we may become more aware of others' impressions of it for a time.
