Is that the same Websters that tells us the definitions of irregardless, and ain't? Note too that they incorrectly cite "ain't" as a contraction of "are not."

They state that the etymology of "ain't" is a contraction of "are not". I would guess that whether "ain't" was first used as a contraction of "am not" or "are not" is lost somewhere in the fog of history. They correctly state that today it is used as a contraction of "am/are/is not".

"Aren't" is the contraction of "are not."

And that precludes coming up with any other contractions (or contracting a contraction even further)? "Aren't" still contains one of those hard-to-pronounce "r"s.

"Ain't" is the slang contraction of "am not," originating in the drawled dialects of the U.S. antebellum deep south.

Phonetically, I think it's easier to connect "are not" and "ain't" (my drawling skills are somewhat lacking, I'm more used to "fast Hoosier with German accent"), especially by going "are not" -> "aren't" -> "ain't".

All of the other dictionaries I checked als define "carrot-and-stick" as "reward-and-punishment", for example these guys:

http://dictionary.cambridge.org/define.as....stick*1+0

They also label "irregardless" as "Non-Standard", and avoid dwelling on the etymology of "ain't".