Babies are so passe, even royal ones. The hip new thing to have is a “theyby”, according to a trend spotted by New York magazine that sees parents bringing up their offspring in a gender-neutral fashion.
There was of course nothing gender-specific about the “ba-“ part of “baby”, which is already a diminutive form of the original English word “babe”. The Oxford English Dictionary says that its origin is probably onomatopoeic – two syllables of “ba”, which is a typical “early infantile vocalisation”. So while a baby can call itself a baba, even if by accident, it will take much longer to pronounce itself a “theyby”.
So “theyby” here points to the desired attitude of others, rather than removing any bias from the traditional description of the object in question. (It is often unimportant whether such bias really existed anyway: replacing “mankind” with “humankind” hurts no one.)
Meanwhile, the possibilities for today’s theybies seem endless. If they need looking after they can go to theycare. In time they will even eat gender-neutral smoked-pork slices (theycon) on a Saturday morning while reading a language column in a theyper.