According to A Collection of College Words & Customs by Benjamin Homer Hall, written in 1856 I believe, gas is defined as cheating or deceiving someone. Any ideas why that may be?
In “The Oxford Dictionary of Current English” (Clarendon Press 1919), one of the definitions for “gas” is:
empty talk, boasting, humbug, windbag eloquence
“Humbug” isn’t defined in the same document, but the current Mirriam Webster dictionary defines it as:
hum·bug noun \ˈhəm-ˌbəg\
: language or behavior that is false or meant to deceive people
: someone or something that is not honest or true
So it appears that’s the link: “gas” is “empty talk”, associated with “humbug”, associated with “intentionally deceptive language”.