For example, "dude," "man," "buddy," "pal," etc, when used to stand in for someone's name. "Hey, pal, how's it going?"
Is there a word for terms like these? Or is "colloquialism" as close as we can get?
What you’re talking about are informal forms of address, colloquial vocatives, faux intimates, or my favorite from William Safire, hailnames. They’re forms of direct address (hence vocatives) used in casual situations as a substitute for you or for the formal sir or ma’am (depending on gender).
The reason Safire calls them hailnames is because they’re most famously used when you’re hailing someone to get their attention, as in Hey X, could you. . . ?” Or “Listen X, . . .” Some of them have other, non-vocative uses, and a few can be prefaced with my.
There are oodles of these, but most of them occur only between men, often young men, in casual situations. Many are strictly regional. Some say something about the age, sex, race, education, or social class of the speaker or the person addressed. Others carry a tone of irony, aggression, or condescension. They impose a faux intimacy if used on someone you don’t know, something many take offence at.
Here’a a small sampling of these hailnames, almost all of which risk being hot buttons of hate for the uninitiated:
Whenever you address someone by something other than their name or the pronoun you, you risk offending them. Name-calling is risky business indeed.
It is impossible for the non-native to judge the appropriate connotation of these for any given situation. Even for native speakers they risk coming off as artificial or insincere; for non-native speakers, they are a mine field of assured self-destruction that may well get you sneered at or even punched in the face.
Since so many of them are regional or from one particular subculture, whenever someone with an accent other than the region they come from uses one of these, it sounds fake. Fake is bad.
You have been warned. Just don’t do it.
A term I have seen used but that tchrist has not been mentioned is familiarizer, referring to words inserted in speech in order to solicit or emphasize social solidarity. Geoffrey Leech has a 1999 piece which contrasts it with other vocatives:
Oh yeah dude totally. (AmE)
Since the familiarizer dude here is in the middle of an ongoing exchange, it cannot have an attention-getting or addresss-identifying situation, and so appears to have a purely social bond-maintaining function.
They aren't always used as terms of endearment, of course (I'm not your friend, buddy and so on): not so fast, sweetcakes or now look here, kemosabe or we've been waiting, homeslice almost certainly intend to express hostility or intimidation. I have heard this described as the contemptuous familiar, but as it does not seem to feature in my search results, it may have been a humorous nonce usage.
It seems to me that colloquial appellation fits well here, sounding less abstruse and technical than colloquial vocatives, faux intimates, or hailnames.
a name or title: As a child, he received the appellation "Mouse".
A search for colloquial appellation in the massive EnTenTen corpus of Sketch Engine yields only three results, but all appear to be in academic contexts of different kinds.
Another word for such expressions is 'salutations', although like 'form of address' etc. the expressions sound too informal for this title.