Yeah, the whole "Jack" thing was big during the house explosion of the late 80's. I remember a song called "Jack Le Freak" that was a house remix of Chic's "Le Freak" with the Jack sample added in. Also, another big record at the time with that "Jack...jack...jack" echo sample was "I Want to Be Your Property" by Blue Mercedes (you can hear it on You Tube. Just search for "Blue Mercedes 1987" and play the first result that comes up).
I'm also pretty sure it was just a hook that was sampled and became linked to house music and was used to mean "move" your body. And speaking of the dance stations you mentioned; as you know, I'm from East Tennessee, and I was a rabid fan of WTNZ in the late 80s. They still remain one of my all time favorite CHR's. Sure they were a small, pretty much broke, class A, rimshot station, but they were amazing. They were on the air from 1986 to 1988 (my senior year in high school and my first two years in college at U.T.). And I listened to them from morning till night time. One reason I loved the station was that I was becoming a big fan of dance during the house/freestyle/hiNRG boom in the late 80s, and WTNZ was the only place in town to hear it. Crosstown WOKI "I100" (which I know you loved, but honestly I hated that station during the Brother Clay, I100 years), completely ignored dance in favor of constant hair bands. I found out about dance while visiting other cities and listening to stations like WQHT "Hot 103/97" New York and WHLY "Y106" Orlando. And I couldn't believe it when 'TNZ signed on and someone in Knoxville was actually playing the stuff I loved.
I remember Saturday nights were the best and were always a "must listen" for me and my friends when we were out cruising. Because every Sat. night, WTNZ ran Jeff Wyatt's syndicated "American Dance Traxx" countdown followed by TNZ's own Saturday night dance party that lasted till midnight or so. They played some dance throughout the week, but they really got into it on Sat. night. You would hear tunes like the Blue Mercedes song I mentioned above, along with stuff like Mel and Kim "Showing Out" and "Respectable", Bomb the Bass "Beat 'Dis", S-Express "Theme From S-Express", American Soviets "C.C.C.P.", Kylie Minogue "I Should Be so Lucky", Sinitta "Boy Toy", Georgio "Lover's Lane", etc. (check all of these out on You Tube, if you've never heard them.) Also, they played all the Latin Freestyle stuff too like Will to Power "Dreamin" and "Say it's Gonna Rain", Noel "Silent Morning" and "Like a Child", Debbie Deb's "Lookout Weekend", "When I Hear Music"
and "I'm Searching", TKA "One Way Love", "Louder Than Love", and "Tears may Fall", etc. etc.
Ok, I'm rambling, but it was a great time for dance music and I wish it would happen again. And WTNZ was a great station that kept me connected to the music I loved, and that was very hard to find in Knoxville. (remember, this was way before the internet and satellite radio, so it was really hard to hear this music unless you were in the northeast or Florida where it received a lot of airplay. Thats why I listened to and taped songs off of WTNZ so religiously. (I only wish I had saved more. I only have a few snippets and short chopped up airchecks from them). I'm sure you already know the history of the station, but they began as "95-3 TNZ" or "Knoxville's Tennezzee" during 1986 and later evolved into "Power 95" during their last year from 87 to 88. They were a bit more dance friendly during the "TNZ" phase, but they still played a lot of dance and rhythmic stuff as "Power 95", that crosstown I 100 never touched. And they actually were pretty successful. The reason they went off the air was due to the owners going bankrupt. But ratings wise, they managed to pull almost a 5 share and came within a few tenths of a point of beating I 100 during their last book in '88. (And this was a class A rimshot up against a full class C 100kw stick at WOKI). So they certainly had a following. That's why it was so sad that they went bankrupt and went dark in the fall of '88, just when they ratings had really started to take off. Anyway, sorry for the long rambling post, but the mention of WTNZ always gets to me.
(Also, on a sidenote, WTNZ was home to many well known area personalites during their younger days. Tom Miller now at Citadel and WIVK, John Wilkerson now at WNML "the Sports Animal", Kim Hansard, now mornings at CHR "Star 102.1" Knoxville, and of course, Mike Keith the play by play voice of the Tennessee Titans. All of them got their start as dj's at 'TNZ. (My favorite was always the late Jeff Freeman and Mike Keith who did mornings and then afternoons as a team. "Freeman and Spike" with Screamin' Jeff Freeman and Mike "Spike" Keith was must listen radio and one of the best CHR shows I've ever heard).
Anyway, sorry you never got to listen to them when you were in the area back then, but you truly missed out. As I said, I hated I 100 at the time because they ignored dance and rhythmic stuff, but I lived and breathed 'TNZ. Check out some of those first few songs I mentioned to get a good feel of how dance sounded during the late 80's. Bomb the Bass, S-Express, Blue Mercedes, and American Soviets are all huge personal favs of mine from back in the day when I first got into dance music.
Boy have things changed since I first worked in radio in the late 80's doing small town country radio and actually using turntables and 45's