Dude is a slang word that's been around for decades now. It is usually used as a noun to refer to someone, whether that person is your best friend or your dad. I think that's what’s wrong with our culture today though, that we have no respect for our elders and instead of addressing them with a proper title, or as our elder not our buddy; we sue the word dude.
It originated in the late 19th century from the Germans, and in context was originally used as anther word for fool. It then morphed into a term to refer to men who seemed to be overly obsessed with how they dressed and keeping up with the latest fashions. But in the more American sense it was started in the late 1800, in New York. It was the short hand term for the phrase, ’Yankee Doodle.’ It was then applied to the ‘city slickers’ who would go vacation in the west. Hence ‘dude ranch’ It was originally a gender specific term to males. The females were never referred to as anything more than ‘woman’ for the first few centuries of the Americas. The word then started becoming gender neutral, and anyone and everyone would use it on their friends. Now a days this word if used to refer to everyone and his brother. It just rolls off the tongue. I don't even realize I call my dad dude half the time because I refer to everyone else like that.
Originally spelled ‘dood’ then morphing into our current form of dude; it was essentially just a tool to make fun of people. Like the way we use the word hipster today, “look at those big round glasses and tight jeans with the rips and the blazer on top, she’s so hipster” maybe we should bring back ‘dood’ in that context since it only took us about 10 years (a decade) {idk which sounds better} to wear out the word hipster. Or we could go way back and just call everyone a doodle.
Solidarity without intimacy (cite) this is essentially the deeper meaning of the word. Its used when you’re trying to say you know someone, they’re a friend/acquaintance, but not your best friend. You’re tight enough to call them dude. There are so many connotations associated with the word. When you do something really cool and you yell “duuuuudee” to make sure everyone around you just witnessed the same thing. Or if your friend did something stupid and you respond with a firm, “Dude.” Or if you see a friend in passing and you’re being nice saying hi, “whatsup dude.” These more recent uses of the noun developed later in the 1900s around the pacific side of the Americas. The suffer dudes coined these definitions. It used to be a connection between the guys. You knew if you were in the crew if they called you dude. Even though the word has fallen into a gender-neutral role in society, there is still a sort of masculinity to it.
http://www.slate.com/blogs/lexicon_valley/2013/11/05/dude_etymology_of_the_word_is_traced_to_doodle_as_in_yankee_doodle_dandy.html
http://www.etymonline.com/index.php?term=dude
http://www.theatlantic.com/magazine/archive/2013/11/dude-transcends/309528/