The Merriam-Webster dictionary (which is a book that explains what words mean) defines “to recruit” as:

To secure the services of

With alternative verbs being “engage” or “hire”.

In other words, if you’re trying to get me to work somewhere, you are trying to secure my services, ergo: recruiting.

And since the -er suffix turns a verb into a “person or thing that does an action indicated by the root verb”, then, if you are recruiting, you are a recruiter.

You can’t just jump to conclusions like that!

I can, it’s called logic. Two consecutive applications of modus ponens, to be exact. If this is too complicated for you, you have no business hiring developers.