Our younger kiddo went through a period of calling his big sister "gago" because he couldn't pronounce her name. Her opinion of this was a long-suffering sigh and "I'll be whatever he can say."
I notice that this developmental process makes categories.. 'differentiable'?, or iteratively improvable, which is often really important. Shows a preference for starting broad, then narrowing in later.
I wonder if we should consider teaching children the word "sibling" before we try to teach them the names of their siblings. We do that with parents, however, we do it because and despite the fact that they'll usually only have one mama or papa so it doesn't really count. Except, it may make it easier to have the insight that other people have their own parents, including their parents.
Our daughter went through a fairly long period of calling cats "dog", and would aggressively correct us if we tried to correct her. Possibly something of the same thing.
I've never known how to make sense of the lack of humility people have about word definitions, especially when it's children.
Since words don't have objective meanings, I wonder if they're kind of reporting an experience that they're having, on which they really could speak authoratatively, something like "Trust me, from the perspective of a learner, the distinction between cats, and dogs, is simply too subtle, and insufficiently important, for the English language to continue to demarcate it. History will come to agree with me."
When we have multiple ships built along similar designs, it's customary to refer to them by the initial example of the design. For example, the last American battleships are called Iowa-class, after their lead ship the Iowa. Until recently, Nora (22mo) used this in naming people. This included, at various times:
Lily really didn't like being called "Anna". Possibly Lily would have minded less if I'd been able to teach Nora to say "Anna-class", but I doubt it: the real hurt was not being the class exemplar. Nora also had a period when she would correct us: whenever anyone said "Lily" she would firmly say "Anna!"
This system makes a lot of sense when you consider how few words she had to work with. Much better to allocate just one of your ~10 words to siblings, and you don't hear the word general word (ex: "sibling") enough for that to be the word you use.
(The post's title would be confusing, except that we've had Classless Inter-Domain Routing for thirty years now.)