There seem to be two meanings of “unexpected” not being differentiated here:
1) name-derived terms like Debian, or the French ‘poubelle’ in the comments, which have become genericized to the point where most of its users don’t know the derivation
2) a more interesting subset of (1), like PageRank, or Lake Mountain in the comments, where part or all of the name itself looks like a normal word appropriate for the situation. (a related concept is nominative determinism https://en.m.wikipedia.org/wiki/Nominative_determinism)
We can add a third one where the name comes from a person that was likely named after a place, which is why it looks normal (Westlake, Outerbridge).
And for #2, most of them are surely done knowing that there's a double meaning, but the origin has been left behind. There's probably a few names that are now more associated with the person than the original pun.
I agree with your distinction, but for a long time I wrongly believed the -ian in Debian was a suffix meaning "relating to" as in reptilian or antediluvian. I didn't have a guess what the first part meant, but I thought it might be a nonsense syllable.
1) name-derived terms like Debian, or the French ‘poubelle’ in the comments, which have become genericized to the point where most of its users don’t know the derivation
2) a more interesting subset of (1), like PageRank, or Lake Mountain in the comments, where part or all of the name itself looks like a normal word appropriate for the situation. (a related concept is nominative determinism https://en.m.wikipedia.org/wiki/Nominative_determinism)