It is a friendlier and more colloquial version of "alright". It is also heard in the exclamation/interjection "Alrighty, then!". I usually hear it at the end of conversations in Canadian English, probably same in American English.
I don't know if it is used in British English. It might be synonymous to right-oh/right-o which is more of a Brit or Aussie term.
I believe that the -y suffix serves to form a diminutive version of alright. But, it is usually attached to nouns.
So, how did "alrighty" emerge as an alternative to "alright"?
Things got more interesting when I did some research about its first usage. The first usage I have found is mentioned as a proper name of God and compared to Almighty.
We English speaking people, ninety millions strong, term our Maker the Almighty. He in whom is all, may, power, might, but it would be no less correct to call Him the Alrighty. He in whom is all right, seeing that in the rebel creature there is a perfect forfeiture of all rights.
[Calvinism popularised By Harry Alfred Long (1879)]
The above passage is from a dialogue in the book and the opposite side thinks that Almighty has a comical and profound sound about it and displeasing to religious taste. Though, the guy who came up with the term "Alrighty" thinks that it is a better translation of Despotes than Lord is.
Alright, this term can be considered a neologism but it was worth to mention. It is even mentioned in some other sources. I don't know if there is any connection.
Then, the second usage I found is a lot like to our version. It takes place in a dialogue again:
'I didn't mean that."
'Yes, you did; I am heart broken."
'Poor boy; forgive me."
'Alright."
'Alrighty."
'Well, I must be going."
'What for?"
'Just 'cause I said so."
'Is that it?"
'Yes."
'Well, goodbye."
'Goodbye."
'Say there."
'What?[A Missourian in the Far West; Or, The World as Seen by a Stranger by Joel Strother Williams (1906)]
And finally I found an explanatory entry as an adverb:
[Dialect Notes, Volume 4 University of Alabama Press, 1913]
Though, it seems like it is used as an "okay" here. I'm not sure if it is still used in this sense today. There is a hint saying that it is in widespread college usage.
Did I just answer my own question? I'm not sure, still. I need someone to sum it up or clarify. I may have missed some points also.
In summary, can we say that it naturally emerged in college jargon and entered in magazines first in early 1900s? Is this a valid deduction?
Best Answer
Google Books searches find three strands of use of alrighty in the late nineteenth and early twentieth centuries: as a translation of despotes in biblical translation; as a form of pidgin English used by natives of other lands; and as an American English form that appears to have originated in
'Alrighty God'
The Calvinism Popularised (1879) instance of Alrighty looks to me to be an outlier. Even Henry Long, the author of that work, concedes what may have been the strongest objection to it, immediately after the language that ermanen quotes from it in the question above:
A Dutch speaker quoted in Transactions of the International Dental Congress (1905) seems to echo Long's views:
But a Google Books search suggests that no one took Long's advice to replace Lord with Alrighty in their translations of the Bible into English.
'All righty' and 'alrighty' as dialect forms of 'all right'
Following Henry Long's book, the next-earliest instance of the term in a Google Books search appears as all righty and appears in Mary Owen, "The Taming of Tarias," a story set in 1840 in Kentucky, in The Century Magazine (December 1889), where the character using the wording is a young white woman named Jincy King:
Similarly, Ellen Kirk, Dorothy and Her Friends (1899) uses the term as dialect speech by native English speakers:
The fishermen have names like Sam Perkins, Ben Coe, and Ned DeForrest, so they are not supposed to sound exotic.
The earliest instance of the single-word spelling alrighty in the sense of "all right" or "okay" is in Joel Williams, A Missourian in the Far West (1906), cited by ermanen above.
Harold Wentworth, American Dialect Dictionary (1944) has this interesting entry for all righty:
Harold Wentworth & Stuart Flexner, Dictionary of American Slang, first edition (1960), has this usage note for the various spellings of all righty:
Barbara Kipfer & Robert Chapman, Dictionary of American Slang, fourth edition (2007) has the following update:
'All righty' as pidgin English
One nineteenth-century instance of all righty is from Frederick Williams [Herbert Hamblen], On Many Seas: The Life and Exploits of a Yankee Sailor (1897):
Here the "all righty" is evidently an instance of pidgin English. So are the three instances in Owen Hall, "More Warm Than Pleasant," a story set in New Zealand, in The English Illustrated Magazine (January 1897):
The pidgin usage seems to have faded away as the twentieth century progressed and interest in representing the broken English of non-native English speakers became less prominent in published writing. In any case, it seems not to have drawn any dictionary coverage in recent decades.
Conclusions
The history of 'all righty' and 'alrighty' gets off on the wrong foot with the odd promotion of Alrighty as an epithet for God in Henry Long's religious polemic of 1879. But not long thereafter (in 1890), the term appears in its modern sense in a story set in Kentucky fifty years earlier.
Harold Wentworth reports that the term was in dialect from circa 1890 in Indiana (just north of Kentucky) and later elsewhere in the United States in the early 1900s, becoming college slang at some point. The Dialect Notes entry that ermanen cites in the opening question indicates that college use was widespread by 1913 (significantly earlier than Wentworth suggests), but still one or two decades after the term's initial rural use (probably).