Reading a different question about the opposite of the word *consultant* made we wonder why the word shifted semantically from the asker to the person who answers?

From Etymonline:

> 
> consultant (n.)
>  1690s, "person who consults an oracle," from consult + -ant. In medicine, "physician called in by the attending physician to give consultation in a case," by 1872 (perhaps from French, where it was in use by 1867); general meaning "one qualified to give professional advice" is first attested 1893 in a Sherlock Holmes story. Related: Consultancy (1955).
> 
> 
> 

The structure of the word suggests one who consults (others).

[Consult](https://www.merriam-webster.com/dictionary/consult) means to ask or refer to. *e.g. Consult the experts.*

[-ant](https://www.merriam-webster.com/dictionary/-ant?src=search-dict-box) (and its sister -ent) give the meaning of taking action or agency.

*Attendants* attend others. *Commandants* command others. *Regents* rule others. *Dependents* depend on others. Etc.

How did *consultant* shift from the person asking to the person asked?