watching Black List on netflix, Raymond said to Lizzy (agent Keen):
Strap on your tinfoil hat Lizzy
I am trying to understand what does he means in reality I know strap on means to hold strong but the real meaning I assume is that she has to accept and move forward or so please advise
A tin foil hat is a hat either made out of or lined with aluminium foil (sometimes called tin foil). There is a stereotype of paranoid people wearing tin foil hats to protect themselves from mind reading or mind control by sinister forces. Due to this stereotype, terms like "tin foil-hatter" are sometimes used to describe "crazy" thinking or those who think that way.
Some people – "Tin Foil Hatters" – have a belief that such hats prevent mind control by governments, spies, mobsters, corporations, or paranormal beings that employ ESP or the microwave auditory effect. People in many countries who believe they are "targeted individuals", subject to government, corporate, or criminal spying or harassment, have developed websites, conference calls, and support meetings to discuss their concerns, including the idea of protective headgear. Vice Magazine wrote that the tin foil hat in popular culture "can be traced back in a very weird and prescient short story written in 1927 by Julian Huxley" titled "The Tissue-Culture King", wherein the main character uses a metal hat to prevent being mind controlled by the villain scientist. Over time the term "tin foil hat" has become associated with paranoia and conspiracy theories.
"Strap on" in the sense used here, means to firmly attach something, e.g. a bicycle helmet may have a strap to keep it firmly secured to your head. So Raymond is telling Lizzie to metaphorically put on her tin foil hat and keep it there, with the intended meaning being that they are going to have to start thinking in crazy, paranoid ways to understand the mystery.
Some people worry about electromagnetic radiation affecting their brains. In extreme cases, people may think that such radiation can be used to control their thoughts, read their minds, etc. A commmon stereotype (based on a bit of truth) is that some of those people fashion tinfoil hats, believing that the metal will protect their brains from the radiation.
Raymond is saying to Lizzy that they are going to encounter a situation involving such people, presumably wacky conspiracy theorists and others with far-out ideas. Raymond doesn't literally want Lizzy to put on a tinfoil hat, and he doesn't believe that such hats are actually effective. He is making a comment about the kinds of people or situations that they are going to encounter.
To "strap on" means to attach something to something else by means of a strap or straps. In this case a hat or helmet with a strap or ribbon securing it under the chin.
A "tinfoil hat" is a device supposedly worn by those who are paranoid to protect them from radiation or government mind control or similar delusion. It is often used as a joke when referring to people who worry about non-existent problems.
I've never seen the series you are talking about, but I assume Raymond is saying (in a light hearted way) that Lizzy should take precautions or beware of some danger. He is not telling her to actually put on a hat made from tinfoil.
A similar phrase would be "We are going to have a bumpy ride" - we are not necessarily going on a journey, but things are going to get difficult or dangerous.
There is a trope in science fiction about tinfoil hats which are supposed protect the wearer from bad rays. Also, it is used in comedy to connote a person who is slightly nuts as the person believes they are being targeted by, say, aliens.
strap on is just a phrasal verb. Helmets often have under-chin straps. So, here the tinfoil hat has a strap for purposes of sarcasm. Usually, tinfoil hats would not have a strap. That is what makes of funny or icily sarcastic.
Other things can be strapped on also. For example, a construction worker can strap on a toolbelt around his waist.
Strap on a helmet strap on a gun
So, it sounds like the character is saying: Oh my, this could be dangerous but is saying it in a sarcastic way. In other words, not really dangerous but we need more context to determine what exactly is going on.
