Right, 'Sulawng' was probably kicking around for a bit before it entered the world of the print under the two-word english spelling that we know today. It popped up in the 1860 version of a poetry book by Walt Whitman called 'leaves of grass'.
When Whitman's friend and fan William Sloane Kennedy, wrote about it much later in 1923 this was what he had to say:
The salutation of parting—‘So long!’—was, I believe, until recent years, unintelligible to the majority of persons in America, especially in the interior, and to members of the middle and professional classes. I had never heard of it until I read it in Leaves of Grass, but since then have quite often heard it used by the laboring class and other classes in New England cities. Walt wrote to me, defining ‘so long’ thus:
|"A salutation of departure, greatly used among sailors, sports, & prostitutes—the sense of it is ‘Till we meet again,’— conveying an inference that somehow they will doubtless so meet, sooner or later.”|
|...||... It is evidently about equivalent to our ‘See you later.’ The phrase is reported as used by farm laborers near Banff, Scotland. In Canada it is frequently heard; ‘and its use is not entirely confined to the vulgar.’ It is in common use among the working classes of Liverpool and among sailors at Newcastle-upon-Tyne, and in Dorsetshire. ... The London Globe suggests that the expression is derived from the Norwegian ‘Saa laenge,’ a common form of ‘farewell,’ au revoir. If so, the phrase was picked up from the Norwegians in America, where ‘So long’ first was heard. The expression is now (1923) often used by the literary and artistic classes.|
So clearly, although Norwegian looks like a strong candidate there was no agreement on the origin of the phrase even that far back. It's interesting that Mr Kennedy seemed to believe that it originated simultaneously on the coasts of America and in industrial towns such as liverpool, as well as Scotland and Canada in other words places with large irish immigrant irish populations (Whitman's poem was penned only about 20 years after the potato famine) or places with an influence of scots gaelic (which is basically the exact same language as Irish anyway).
Right, "sulawng" continues to have an obscure origin as none of the theories postulated stand up to any scrutiny for any length of time, I'm gonna fast-forward to 2005 and the publication of this article which sums things up as follows:
ADIEU, BYE-BYE, CHEERIO:
THE ABC OF LEAVE-TAKING TERMS IN ENGLISH LANGUAGE HISTORY
So long –
The OED (s.v. long) vaguely writes in brackets: “Cf. G. so lange.”
Mencken’s information (1919/1963: 192 & 258) is a little contradictory: at first he categorizes So long as a Germanism, later in the book he classifies it as “of English origin” (or does he want to say that the term is of German descent, but that it came to America via England?).
According to Terasawa (s.v. long) we would have to postulate an imagined starting-form *(it will seem) so long (until we meet again). Under the entry so long itself this hypothesis is preceded by a question mark, and the hypotheses of a German origin (So lange ‘so long’) and an Arabic origin (salấm ‘peace’) are also given.
Also in Weekley (s.v. so long) we find the hypothesis: “? Corrupt. of salaam.”
The German origin is also offered as one possible explanation for the expression with “origin unknown” by Chapman (s.v. so long); in addition, Chapman writes: “perhaps fr[om] Hebrew shalom and related Arabic salaam, both greetings meaning ‘peace’; perhaps fr Irish slan ‘health,’ used as a toast and a salutation” .
You can see why it's still bottom of the list cant you? First of all "slawn" it's spelt like an English word, as "slanne" and second of all he's taken it for the literal meaning, 'health'* instead of the way it's actually used as 'goodbye' - but wait, there's more:
although a more accurate translation is 'safe','health is 'Sláinte' which is used as a toast or salutation
He then quotes William Sloane Kennedy (in full above) and sets about figuring it out once and for all.
|I first consulted Fraser and Gibbon’s dictionary on sailor slang (1925); but the phrase wasn’t listed there. But if it is true that the term originates in sailor slang (and from there was first spread among other social groups in contact with them, e.g. soldiers and prostitutes), then we can give the following comments on the various suggestions.|
Although the German hypothesis is formally possible, it must be underscored that
there is no hint that a German leave-taking expression So lange ever existed (cf.,61e.g., DW).
A Hebrew (or Yiddish) origin seems unlikely for a sailor term.
The Arabic hypothesis seems possible for a sailor term.
However, it has to be underlined that Salaam is used both as a greeting and a leave-taking term, while So long is only used as a leave-taking term.
The Norwegian hypothesis seems also possible for a sailor term.
And indeed, in Norwegian leave-taking phrases such Adjø så lenge! Farvel så lenge! Mor’n så lenge!,
literally ‘Bye so long! Farewell so long! Morning so long!’,
the iconeme being something like
“farewell for the (long) time being until we meet again”.
The first part was clipped and the second represents a loan translation.
So in conclusion, the Norwegian origin,
though not included in the modern etymological dictionaries,
can be regarded as the most probable etymology
And that's where it stands, all perfectly logical on paper, and when the poor eejit has no knowledge of either the pronunciation or the use of 'Slawn', you can see how he opts for the Norwegian hypothesis as the most likely.
With a correct understanding of 'slawn' in the irish sense, I believe it makes a far more compelling candidate because unlike Adjø så lenge! Farvel så lenge! and Mor’n så lenge! 'slawn' needs no clipping: it is used as an extant and complete phrase for farewell.
Yes, it doesn't look half as good as 'så lenge' does on paper,( also two words, only the vowels are different) but here's the thing: Sailors, prostitutes and the immigrant underclass of the nineteenth century didn't communicate with paper quite as often as they did with sounds.
"Slawn" (as pronounced by an american which is the way Whitman would've heard it ) does sound almost exactly like an american saying "Suhlong"; neither of them sound remotely like "Zuhlengya".
listen to it on google translate and make up your own mind
Or try singing this:
Nowhere near as good a match is it?