“Ciscoan” is the name of an inhabitant of Cisco, Texas. The name “Ciscoan” has been cited in print since at least 1893.
   
 
Wikipedia: Cisco, Texas
Cisco is a city in Eastland County, Texas, United States. The population was 3,851 at the 2000 census.
 
The Portal to Texas History
6 May 1893, Fort Worth (TX) Gazette, pg. 1, col. 2:
HARD AT WORK.
Are the Brave Ciscoans Building Up.
Cisco, Tex., May 1, 1893.
 
31 July 1901, Galveston (TX) Daily News, pg. 6, col. 5:
Two to one Cisco could secure the whole business if all Ciscoans would unite on one thing at a time and work it up.
 
1 April 1920, Lubbock (TX) Avalanche, pg. 20, col. 1:
Down Cisco way last week, the owners of the barber shops decided to reduce the cost of barber work, and all of the barbers walked out, leaving their employers without help to carry on their business, and many a Ciscoan went without a shave or hair cut for several days.
 
The Portal to Texas History
11 January 1923, The Optimist (Abilene, TX), “College Basketball Season Opens Friday,” pg. 1, col. 5:
It is rumored that Cisco Christian has a good team and that the Wildcats may have a stronger fight in tomorrow’s game than was afforded them in football when the Ciscoans were swamped under a heavy score.
   
1 March 1926, Dallas (TX) Morning News, “West Texas Druggists Are to Meet at Cisco,” pt. 1, pg. 11, col. 1:
Ciscoans who went to Stamford and who are responsible for the city’s victory over the other aspirants are Messrs. Ben Young, Bob Bettis, J. E. T. Peters, M. W. Holder and E. O. Elliott.
   
Google Books
I Give You Texas!:
500 Jokes of the Lone Star State
By Boyce House
San Antonio, TX: The Naylor Co.
1943
Pg. 67:
But Cisco is enterprising, too.
 
Rival editors declare that if a man on the “Sunshine Special” jumps off at Cisco, grabs a ham sandwich, jumps back on the train, continues on to California and— ten years later— he is killed by a truck or elected to Congress, the Cisco paper refers to him as “a former Ciscoan.”