None of the names go with the .io extension because they're plural. .io is synonymous with tech. Singular words are empty vessels and can mean anything (usually) so they can match the .io even when they're not particularly techy.
But once you add the s they become commercial words.
Crab would be a great name. $5k-10k for the right end user. But crabs .io is all but worthless. Maybe someone would come along for a few hundred but it's unlikely. Not to mention that crabs is an STD.
Rabbi - I could see this being used as something unrelated to rabbis, but I don't know. This is a tricky one.
Tomboy - Doesn't really exude anything tech, and its too specific a word to be an empty vessel.
Mulan - Probably trademark issue.
Bongo would be a great name. Probably 1-3K if you're lucky, maybe more. But same thing as crabs .... the plural version kills it.
Due the high price of renewing .io names, you have to be very selective about what you register. None of these names I would keep in my portfolio.
Disclaimer - These are just my opinions and I could be totally wrong about everything.