Ablaut Reduplications

bric-a-brac, 
chit-chat, 
criss-cross, 
dilly-dally, 
ding-dong,
fiddle-faddle, 
flimflam, 
flip-flop, 
hippety-hoppety,
kitcat,
kitty-cat, 
knick-knack, 
mish-mash, 
ping-pong, 
pitter-patter,
riff-raff, 
rickrack, riprap, 
see-saw, 
shilly-shally, 
sing-song,
snicker-snack, 
splish-splash, 
teeny-tiny, 
teeter-totter, 
tic-tac-toe,
tick-tock,
ticky-tacky, 
tip-top, 
tittle-tattle,
wish-wash,
wishy-washy, 
zig-zag