Changing the suffix of the name of a compound loses one hydrogen atom?

I just chanced upon these intriguing pubchem entries: [Ethyl Carbylamine](https://pubchem.ncbi.nlm.nih.gov/compound/4474585) and [Ethyl Isocyanide](https://pubchem.ncbi.nlm.nih.gov/compound/Isocyanoethane#section=Top). Their structures - as given on that site - are respectively:


[![enter image description here](https://i.stack.imgur.com/tGJ9M.png)](https://i.stack.imgur.com/tGJ9M.png) and [![enter image description here](https://i.stack.imgur.com/NCrqx.png)](https://i.stack.imgur.com/NCrqx.png).


Notice that the only difference is the H atom on ethyl carbylamine, which is missing in ethyl isocyanide!


I always understood *carbylamine* and *isocyanide* being interchangeable suffixes for an IUPAC name, but it seems like I've been proved wrong.



> 
> What is the reason for such an anomaly in the structures of these two compounds?
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