I guess I have a problem with all of them:
ABS: Reminds me of brakes (who wants to put the brakes on tickling?)
TUMMY: Reminds me of an antacid.
MIDSECTION: Reminds me of the place two streets come together. (Not that there's anything wrong with coming together).
BELLY: Reminds me of belly ache...which brings us back to the need for an antacid.
STOMACH: Reminds me of stomach ache. There's that antacid thing again. (Stomach ache is my wife's usual excuse, as in, "Not tonight, I have a..." No, wait...that's HEAD ache). Maybe stomach's not so bad.
MIDRIFF: I don't believe I've ever heard this term, with the exception of the Playtex Girdle, which cured midriff bulge. If a guy is going to have a bulge, he would prefer that it not be in his midriff.
😀