"why" can be compared to an old Latin form qui, an ablative form, meaning how. Today "why" is used as a question word to ask the reason or purpose of something. This use might be explained from a formula such as "How does it come that ...". If you meet an old friend of yours, whom you never expected to meet in town, you can express your surprise by saying: Why, it's Jim! This why in the ...
11 Why is it that everybody wants to help me whenever I need someone's help? Why does everybody want to help me whenever I need someone's help? Can you please explain to me the difference in meaning between these two questions? I don't see it.
Why is a just a rather odd wh -word. Its distribution is very limited -- it can only have the word reason as its antecedent, and since it's never the subject it's always deletable. Consequently it behaves strangely, as you and others point out.
Can "why" be a conjunction? - English Language & Usage Stack Exchange
Why have a letter in a word when it’s silent in pronunciation, like the b in debt? Can anyone please clarify my uncertainty here?
Possibly relevant to why /z/ won: if I try to pronounce axis with a /z/ instead of an /s/, it sounds hardly at all different. Someone with a better understanding of phonetics can probably explain why the contrast is so small in that context.