flim_flam considers a particular way that words and phrases are built up uses a form of "reduplication" in which a syllable, word or phrase is repeated, but with a single vowel sound changed. A simple example of such a pattern is the phrase "flim flam". Usually, both vowels are "soft", but the examples of ship shape and teeter totter show that this is not always the case.
Bali belly (traveler's sickness in Indonesia)
bibble babble (babble)
Cancun (a resort town in Mexico)
chiffchaff (a bird)
chit chat (idle conversation)
chitter chatter (idle talk)
cling clang (an imitation of the sound of bells ringing, or
other metallic ringing sounds)
clip clop (an imitation of the sound of a horse on a street)
clish-clash (gossip)
coon can (a Spanish two player card game of making sequences)
crinkle-crankle (winding, circuitous)
crinkum-crankum (something full of twists and turns; the vagina)
criss cross (an interlacing pattern)
dib dab (a sailor)
dib dabs (delirium tremens (the shakes))
dibble dabble (noisy splashing; rubbish)
diddle daddle (nonsense)
Dig Dug (a video game involving the digging of escape tunnels)
[to] dilly dally (to dawdle)
dimber-damber (a gang leader)
ding dang (a mild expletive)
ding dong (a mild expletive; the sound of a bell; a fool)
dingle dangle (swinging to and fro; the penis)
dish-dash (a kind of Arabic robe)
double dabble (the conversion of data from decimal to
binary form)
fibble fabble (nonsense)
fidfad (a fusspot)
fiddle faddle (a dismissive exclamation; nonsense)
fimble famble (a poor excuse)
fingle-fangle (a trifle)
fixfax (a Scottish version of the stocks, used for punishment)
flicflac (a kind of dance step)
flick flack (a gymnastic move)
fliff-fluff (tousled)
flim flam (the deception used to implement a fraud)
Flin Flan (a town in Canada)
flip flap (a kind of firework; the penis; a sudden reversal)
flip flop (a sandal; to reverse oneself)
flipperty flopperty (loose and floppy)
fonfen (the spiel of a con man)
gewgaw (a gaudy trinket)
gibber gabber (spoken nonsense)
gibble gabble (spoken nonsense)
giff-gaff (give and take; banter)
ginch gonch (underwear)
gourd guard (a helmet)
grim gram (a telegram with bad news)
group grope (a sex party)
hee haw (a robust, rowdy or coarse laugh)
higgle haggle (a confused mess; to haggle)
hip hop (a slightly less shrill version of rap)
hippity hoppity (describing a hopping movement)
hishee hashee (soup and bouilli, an apparently awful meal)
Hong Kong (a port city in China)
jab job (an injection of drugs)
jibber jabber (nonsensical chatter)
jibble-jabble (nonsensical chatter)
jigjog (having a jolting motion)
jiggety-joggety (something strongly rhythmical)
jim jam (to jam; to jazz up)
the jim-jams (delirium tremens; the shakes; pajamas)
jing jang (the vagina)
jingle jangle (money, cash)
jipajapa (a South American plant that looks like a palm)
kim kam (astray; awry; out of order)
King Kong (our hero)
Kit Kat (a club name; a candy bar)
kittle cattle (difficult creatures to handle; unreliable persons)
knickknack (a curio or keepsake)
kniff knaff (a joke)
[to] launch lunch (to vomit)
Lib-Lab (an alliance between the Liberal and Labor parties)
Micmac (a Canadian Indian)
MiMo (Miami Modernism, an architectural style)
mingle-mangle (to mingle in disorder)
mishmash (a formless mess)
mishmosh (a formless mess)
mixter-maxter (a confused jumble)
mixty-maxty (muddled together)
nick nacks (testicles)
nid nod (to allow the head to drop repeatedly from drowsiness)
niddle noddle (having an unstable or wobbly head)
niddy noddy (a two-ended weaving frame on which yarn is wound)
niffy naffy (trifling)
nig-nog (a fool)
ning-nong (a fool)
nitter natter (idle conversation; meaningless chatter)
nyiff-nyaff (to potter about)
past post (to make a bet on a race that has already been run)
pif paf (a card game)
pilpul (subtle rabbinic hairsplitting argumentation)
ping pong (table tennis)
pish pash (an East Indian rice broth made with bits of meat)
pishery pashery (disparaging, trifling talk)
pish posh (a dismissive exclamation)
pitchy patchy (ragged work clothes)
pitter patter (the sound of little feet; the sound of the heart)
prinkum prankum (a prank)
prittle prattle (empty talk)
pussy posse (the vice squad; a group of sexually available women)
rick rack (a kind of zigzag fencing in which rails from
alternate sides are "laced" together)
riff raff (a disreputable group of people)
rimble ramble (nonsense)
riprap (to borrow money)
say so (one's word; verbal authority)
schnicky-schnacky (a public display of affection)
scrip-scrap (odds and ends)
see saw (a teeter-totter)
shilly shally (to dawdle; also "shill-I-shall-I")
shim sham (a feeling of unease or fear)
shipshape (in order; neat)
shit chute (the anus)
sicsac (the crocodile bird)
sick sack (a paper bag intended for vomiters)
sing song (to speak in a way that emphasizes sound over meaning)
skimble skamble (confusingly rambling, wandering)
slipslop (a blundering misuse of a word; kissing; sloppy stuff;
twaddle; bad liquor)
slish slosh (an imitation of the sound of splashing water)
snipsnap (tart dialog)
spit spot (fine, excellent; immediately)
splish splash (imitation of splashing water sounds)
Swig Swag (the joking name of a police investigation into the
theft of 400,000 miniature bottles of liquor)
swish swash (a diluted alcoholic drink)
swishy swashy (wishy washy)
teeter totter (a children's amusement, a see saw)
tew taw (an implement for breaking hemp or flax; to beat or break)
thingy thangy (a thing; an object)
Tic Tac (a candy)
tick tack ( a repetitive sound)
tick tock (imitation of the sound of a clock)
ticky tacky (vulgar and banal)
tiffety taffety (a prostitute)
tip top (first rate)
tish tosh (a dismissive exclamation)
tisty tosty (a ball of cowslips)
tittle tattle (idle chatter; gossip)
trictrac (a game similar to backgammon)
tricktrack (a game similar to backgammon)
trinkum trankum (a trinket; a whim or fancy)
twittle twattle (tattle, gabble)
whim wham (nonsense; a trivial or flimsy thing)
[the] whim whams (a case of nerves)
whimsy whamsy (a whim)
wiffle waffle (an arrogant person)
wig wag (a kind of signaling flag)
wigga wagga (a walking stick)
wiggle waggle (a musical fairground amusement; to sway)
wiggle woggle (a car racing challenge involving many curves)
willie wellie (a condom: a "wellie" is a sort of rubber boot)
wing wang (a joking term for dollars; a piece of burning bark
used as a weapon)
wing wong (a thingmajig)
wish-wash (nonsense)
wishy washy (indecisive)
xiraxara
yimyom (crack cocaine)
ying yang
zig zag (characterized by repeated changes in direction)
Not quite...
vicky-verky (Merseyside)
In a different league:
kitty cat
pitapat
sac and soc