It seems to me that the adjective phrase "regular old" seems to have a few distinct usages, but a confusing conversation and some fruitless searches as to a specific definition have me coming to English Language & Usage SE for insight. I've also gathered some examples from Google Books to try to clarify my question.
Firstly, it seems to connote the meaning "standard", "basic", or "simple", particularly in educational texts:
"Notice how with ArrayList, you're working with an object of type ArrayList, so you're just invoking regular old methods on a regular old object, using the regular old dot operator." 
Finally we've got an A9/C# Which is kind of exotic. To see where this one comes from, start with just a regular old A chord. 
But then it also seems to invoke the idea of being a "true" example of a certain thing--perhaps neither negative or positive.
"You're a regular old image, Jim, says she. I used to laugh at him and call him a regular old crawler." 
(Side note: I think this is the relevant definition of crawler -- 1. a person who tries to please someone in order to gain a personal advantage.)
Although anecdotally, I believe I've heard it in some early films in such a colloquial usage to express amazement or awe, which may support the "truest" definition:
"Why, it's a regular old feast!"
Lastly, it seems also to have a distinctly negative meaning, or at least a meaning meant to downplay, whether through humility or the implication of plainness or mundanity:
When I asked De Vonya to describe her typical day, she described herself as a "regular old lady." She said her life had become very boring since the baby's birth. 
Here's the inverse of that example, meant to show that something is lavish and expensive:
The properties at issue are not just regular old houses. In Cairo, the residence is a 4,200-square-foot, two-level house with four bedrooms, three bathrooms, two living rooms [...etc] 
At any rate, since it seems to only occasionally describe things that are "regular", where on earth did this phrase and the "old" part come from? Is it interchangeable with or related to "regular old-fashioned"? Which, if any of these meanings are accepted definitions?
 : Head First Java By Kathy Sierra, Bert Bates
 : The Acoustic Guitar Fingerstyle Method By David Hamburger
 : Slang and Its Analogues Past and Present: N to Raz By John Stephen Farmer
 : Not Our Kind of Girl: Unraveling the Myths of Black Teenage Motherhood By Elaine Bell Kaplan
 : Congressional Record, V. 148, PT. 13, September 20, 2002 to October 1, 2002 edited by U S Congress