The use of "hey" in North America

Having had my formative years in New Zealand, I was born in South Africa. I vaguely recall when I was VERY young having someone tell me when I said "hey" that "hay is what horses eat".

I got that then it was more when people would yell "hey" across a room to attract attention, and that was considered a bit rude for that purpose.

However in my adult years in NZ and the UK, a casual nod and a "hey", or "hey, what's up?" was a perfectly acceptable greeting.

Having recently moved to Canada, I greeted someone casually with that yesterday to be told again "that's what horses eat". I felt a bit rebuffed, but decided to ignore it until I could research it - ie, ask on here!.

Is this just a North American thing? Or just possibly this individual's view? Same age and gender as me.

Pretty much the only time I remember hearing "Hay is for horses" intended as an actual admonition, as opposed to a lighthearted and humorous response, was in elementary school. I think our teachers used the phrase to remind us that "Hey, Mrs. Johnson" was an inapproriately informal way to get a teacher's attention – that we should try something like, "Excuse me, Mrs. Johnson" instead.

So many people heard that refrain growing up, though, that I've heard it get tossed out reflexively every now and then.

As for what message the person you greeted was trying to send, it's hard to say for certain. I think some people respond to "Hey" that way in an attempt to sound witty, while others may have misinterpreted our lesson from childhood to mean: using "hey" when addressing someone is always rude. In the former case, I don't think anything so trite ever comes off as very humorous; in the latter, it's professing ignorance for language, since the word isn't inherently rude, and isn't even spelled the same as its cow-feed homophone.

For the record, NOAD even lists "hello" among the word's definitions:

You're mixing up two different "Heys" (or the Canadian you greeted is).

The reprimand "'ay is for 'orses" is/was supposed to teach you to say "Pardon?" instead of "Eh?" if you hadn't heard something, and wanted it to be repeated.

The modern American "greeting" "Hey" is really just a variant of "Hi", "Hello", etc. Which is only vaguely related to the long-standing "Hey!" variant of "Hoi!", "Ho there!", etc., used as an interjection, or a means of attracting attention.

From an AmE speaker, 'hey' is perfectly fine in the US, people use it all the time.

I remember hearing that more than once as a child, "Hay is for horses." in response to 'hey'. It sounds like it was supposed to stop you from using 'hey' but it never did. It comes across more as a (not particularly successful) attempt at a clever saying.

It's not formal at all, but also not at all vulgar. Just plain informal.

I believe the negative response, "Hey(Hay) is for horses" is used to be a political ploy. I've seen it used to put down someone as if they were implying that its use is vulgar. A secondary put down might be "Hay? Are you calling me a horse, punk?"

Its used as a way of confusing the person offering the greeting and making them pause awkwardly and question their cultural up-bringing/identity. A good response back might be, "You're not from around here, are you buddy?"