No, this is not a shortening of "dad slacks."  It originated with the DAKS brand of clothing.  They were a British company which manufactured the first trousers which didn't need anything to hold them up.  Now daks is used in Australia as slang for any type of trousers.

To take a dekko is to take a look.

From corner to corner, slantwise, obliquely, or my favorite from America, kitty-corner.

Australian soldier.  A lot of early soldiers were failed miners, but the nickname stuck after they dug many trenches in the world wars.  They dug in and held on.

Is that true?  Can you say fair dinkum?

A man's favourite piece of equipment.

Duvet, a quilt in its cover.  Australians use a lot of different words for quilts. We used to say counterpane or continental quilt or eiderdown or comforter.  Doonas are a lot more common than they used to be but unless you keep the air conditioning on, they cannot be used on the bed in spring or summer, which feels like more than half the year.  See the Australian Writers' Centre article about the origin of the term doona.

Australia.  So named because in the world globe, it is in the southern hemisphere, down under the countries in the northern hemisphere.

Australian kitchen sinks have integrated drain boards next to the sink itself.  Often, dish racks are placed on these for the kitchen user's washing pleasure.

A drongo is a type of bird (which is actually quite a clever bird), but researchers think the insult drongo is based on a racehorse called Drongo that never won a race.

Wimp.  No one seems sure where this word originated.  It might be related to dribble?

To drop someone is to end a romantic relationship.  Seems a bit of a harsh way to do it.

A person who is not very intelligent.  A dropkick in Australian Rules Football is no longer a favored technique.

Most Australians don't know that a duffer was an unproductive mine which was considered to be worthless.  Now a duffer is a luckless person.

Toilet, or room a toilet is in.  Originated from dunnekin, which meant dung house, from when toilets were little buildings outside the main house.  If you want to keep your adult card, never ever say you are going potty.

In the old days, fights were on bare dry ground and a dust-up was a fight violent enough to raise the dust.