The nearest meaning is crash after a drug high [link]
Hangover or other ill physical and psychological after effects as a result of a drug leaving your system and your body craving more. Specifically , this term refers to amphetamines, though it's often used to refer to other drugs as well.
The crash from the speed was so bad I couldn't move from the corner I was crying in for 3 hours, until I found my fifth of jim beam.
In the linked post, the original poster says:
From going from an emotional wreck with bugger all sleep to a happy single man with a huge life ahead of him in 3 days is surreal. How did I do it you may ask? I fucking sucked it up thats how. I focused on the facts not the emotional pain I had experienced all of 18 hours before. I put a call out on facebook to family and friends (my profile is private and only have true friends and family members) and I had a whole village come to my call!
This is essentially euphoric - like euphoric high similar to that from a drug. The answer says this will end soon, and end badly, with a very bad depressive feeling - "a crash", and the asker will need help of friends in making the actual recovery.
UPDATE
February 01, 2018, the OED has recently added the word swag in its dictionary. Oxford Online Dictionaries reports
A new entry has been added for swag, derived from swagger, and used in slang to denote ‘bold self-assurance in style or manner’, or ‘an air of great self-confidence or superiority’. The OED’s first citation for this particular sense comes from the track ‘December 4th’ on Jay-Z’s The Black Album (2003): ‘My self-esteem went through the roof, man. I got my swag.’ This is the fifth OED citation attributed to Jay-Z.
A glossarial example of the word from the previous year, in a self-described dictionary of hip-hop terminology, defined swag as simply ‘walk’.
ORIGINAL POST
(October 12, 2016)
“Obama displayed similar swag and bluster …”
In his sixth State of the Union Address, President Obama said:
We’re upholding the principle that bigger nations can’t bully the small — by opposing Russian aggression, supporting Ukraine’s democracy and reassuring our NATO allies. Last year, as we were doing the hard work of imposing sanctions along with our allies, some suggested that Mr. Putin’s aggression was a masterful display of strategy and strength. Well, today, it is America that stands strong and united with our allies, while Russia is isolated, with its economy in tatters. That’s how America leads — not with bluster, but with persistent, steady resolve (Applause).
From whitehouse.gov, January 20, 2015
The swag appears to be a clipped form of swagger, which the article accuses President Obama of doing. In the speech, the ‘swag’ refers to America standing strong, unafraid of Russia, and determined to enforce sanctions. The bluster, according to the author, is Obama's words whose tone was possibly concealing a threat to Putin. The fact that Obama asserted America did not engage in bluster, was telling the audience that America was not afraid of taking further action if necessary.
bluster
talk intended to seem important or threatening but which is not taken
seriously and has little effect
swagger
to walk, esp. with a swinging movement, in a way that
shows that you are confident and think you are important
Cambridge Dictionary
Best Answer
It's slang, and not current slang.
The girl has a beatnik style: straight hair worn down, a black dress with no ornaments. These point to the beat sub-culture of the 50s and 60s. Daddy-o was used by "beatniks" or "hipsters" in the 50s and 60s as a general term of endearment towards a man. "Dad" could be seen as an adaptation or shortening. The rest of her language is similar: "Don't worry [...] Lady!", "Tiger", "You're the end!" are all beatnik jargon.
It may also suggest that she views Peter as being a "square" (A socially conventional or conservative person). He acts like a dad, by cutting his hair short, and wearing a tie.
This is not current slang, don't use unless you are trying to sound dated.