and where did it come from in the first place?

The is not the question that can be answered with something like "Philosophy is a disease of language"--that would be "What goes wrong in philosophy?", just as one might say "What goes wrong in asthma?" "It's a disease of the lungs"--this is the question "How does it happen?".

Why would we ask this question?

• Because it will tell us what we do philosophy for, the end we have in mind before it becomes a mere habit.
• Because it will tell us what goes wrong that instead of achieving this end we develop philosophy instead.
• Because it will remind us what we meant when we asked questions that we now mouth without knowing their meaning, that is, what is at stake in philosophy.

It seems to me that too much philosophy is instigated simply by other people doing philosophy. This makes me ask for the first cause, for in Homer's time nobody did philosophy as we see it later. Questions posed were answered.

Austin suggests: incorrigibility. Kant: the unconditioned. And this fits with Socrates against the sophists--that is, there is an individually realizable cause for a sophist questioning (say) morality, claiming that there is no unconditioned moral good. And then there is an imperative to defend against it. This is philosophy as a sort of overactive immune system. Compare skepticism (overreaction to dangerous belief, rather than to dangerous disbelief), creduelity and weak-mindedness (intellectual AIDS), science (is/is not a healthy relation to belief).

Also consider Philosophy's birth as natural philosophy. Purposeful inquiries degraded by a series of mistakes?