Properly written: ¡Ay, güey!
It is a very informal Mexican
exclamation, similar to "OH, SHIT!" without the intense level of vulgarity.
It comes from: Ay! - literal
translation of
exclamation in Spanish of "OH!/ Ouch!"
Güey! - refers to "dude / chav" hence why it is informal.
Ay wey, tu jefa esta bien buena. - "Oh, dang!
Your mom is so hot."
Ay wey! Casi me caigo! - "Oh, shit! I almost fell down!"
¡Ay, wey! Ya no tengo dinero. - "Oh dang. I don't have anymore money!"
Ay, wey. Se me pasó el camión. - "Oh, shit. I
missed the bus."
— ¡Ay, güey! — Exclamó Eratóstenes. - "Oh fuck!" Exclaimed Eratosthenes.
**Either spelling is
equivalent to mean the same thing, except "ay wey" is more prevalent in informal writing or among anyone basically (refer back to the fact of being an informal expression). "¡Ay, güey!" is more prevalent in literature but is not exclusive.