A grammarian is a person who studies or is an expert in grammar. A case grammarian would be a grammarian who is specifically an expert on the different cases in grammar.

The adessive case, in grammar, is that case which relates in certain languages to adjacent location.

Between David and him would be the correct grammar in this case.

An absolutive case is a case in grammar used to indicate the patient of a verb's action - or the one who experiences it.

In grammar, the ablative case is a grammatical case used in some languages, including Latin. It typically represents the relationship of movement away from, separation, or instrumentality. In Latin, it is used to show the means by which something is done or the source from which something comes.