It is derived from: "I do not know"
It was changed to: "I don't know"
Then: "I Dunno"
Finally: "Iunno"
> "When did that happen!?"
> "Uh.... Iunno."

学英语单词
acetylenyl
adjustment range
Alfuy
amynthas morrisi
axial cone
B-listness
beastlihood
Bridalveil Falls
bunker bay
busy token
cathedraical
Celles-sur-Belle
circulation of a bank
coiled radiator
compatible monolithic circuit
confanon
Convention for the Suppression of Unlawful Seizure of Aircraft
converter chip
cruisetour
cryptorachischisis
current sensitive colour screen
cut the ground from under sb's feet
cylindrical friction wheel
cytophil
decentralization of population
derzon
dibutylphosphoric acid ester
duipara
executive president
explicit specific
extra-ocular antennae
family pteridaceaes
filling solution
foot hanger
free steering sequence
gallate isoamyl ester
gilvan
gloeosporium musarum cooke et massee
hemo-oncology
Hennezel
ifrane
improvement and repair trade
international convention
jammer transmitter
jocound
kaputin
law of all-or-none
law of refreshment
leap years
lecture-oriented
letterrure
levo-compound
mean water depth
mixed continuous group
Moloundou
monophosphide
multilayer system
muson
nasselline
non cooperation
non-hazardous
normality condition
nozzle orientation
only time
pervicacity
polyenes
printed-circuit
private health care
quadrating
quarrel over the bishop's cope
rachitic scoliosis
Rapa Nui
reinforcing bar cutting machine
ringworm cassias
Ross, Lough
safety significant incident
sample bias
schlitter
scuba-diving
sensory discrimination
sialodochium
sodium cyanide poisoning
specialized fields
spiderhunters
suborder Maniraptora
supply/demand factor
swindell electric furnace
sympathetic nervous trunk
syndrome of dampness-heat in large intestine
There used to be
to yield oneself prisoner
Tsimlyansk Reservoir
two-electrode tube (diode)
unoverridden
unwholesomeness
valamina
validation of a user's identity
wait for you
Weissenberg photograph
Werfenian
Wolfe's method
Zhibiao