I have heard this word in other languages. It refers (in the bad sense) to those persons who are really hard working, study a lot, memorize, but in fact do not have the intelligence knack. They are not wise, but hardworking.
Such a person might be called a grind:-
Informal A student who works or studies excessively.
[American Heritage Dictionary via The Free Dictionary].
This doesn't invariably mean someone not particularly bright, but it carries that implication (they are grinding facts into their head, mechanically and without inspiration).
You might mean "Dweeb".
Know about it here.