Boomerang word (psychology, linguistics)

A boomerang word is a coined phrase for a particular type of word which, when spoken, either to a group or to a given individual, will always return back. The term references to a boomerang in that, thrown correctly, it returns to the user.

Not to be confused with a dyeing the well attack, which uses the same sort of methodology as a boomerang word, but differs in a boomerang word will only work with an individual and/or group that recognises the word previously, where-as a dyeing the well attack will leak the word across a selection of individuals which have not seen the word before.

Usage
When thrown, a boomerang word only returns if the word is thrown properly, that is to say, the right word is chosen, and the particular individual you're looking to find is familiar with the word. This relies on a similar form as depth-charging, but uses a precise or specific word that the individual in question knows, preferably with an exclusive meaning to them only.

For example, say Gramps and Tom privately agree their code word is 'elephant', and 'elephant' refers to some secret document of importance. If either Gramps or Tom hear the word 'elephant', (the boomerang word), correctly implying or referring to the document (the way the boomerang is thrown), either Gramps or Tom will acknowledge, react or freak out to the word (which is where the boomerang comes back).

Now, say Hans has intercepted the word, but both Gramps and Tom are incognito, EG anonymous. He knows where they might be, but he doesn't know who they are specifically. The way to find out would be to use the boomerang word - Hans throws out the word 'elephant' publicly, hoping that if Gramps or Tom spots it, they react (giving themselves away) and thus the boomerang returns, which allows Hans to know who he is most likely dealing with.

How it works
This particular trick (which could be deemed a form of mentalism) relies on two psychological assumptions of human psychology, one of which is egocentricism (the view that other people think and react like you do, in this case, the assumption Gramps and Tom will think their reaction is normal), and the other assumption is the tendency to react when surprised. It also relies on the exclusivity of knowledge and plays off deception to it's own failure (IE Gramps and Tom's secrecy is their own undoing: if everyone knows it, the boomerang word cannot work).

By mentioning the word 'elephant' with context of secret documents publicly, in logic sets, because it was previously secret, the only people who know what it means (besides Hans), is Gramps and Tom, which means only Gramps and Tom can react to the information (because only they know what it means). Everyone else ignores 'elephant' or treats it as normal because to them the word is natural and meaningless and the addition of secret documents random or incoherent. Gramps and Tom will react (presuming everyone else knows the meaning), at which point no-one can understand why they are so bothered, which sets the stage for a group prising attack.

Psychology
Each person, in terms of memory, stores a limited set of word associations, and each association has an emotional attachment. Private words tend to have a higher emotional attachment, especially when secret, obscured or specific references, which causes them to have a higher rate of successfully causing a reaction.

This would be akin to an interviewer looking an accused murderer dead in the eye with the claim they have evidence they committed the crime. At this stage, a guilty person with weak willpower will likely crack and admit to it (because they know they committed the crime, and the evidence of such causes the memory to return, and thus guilt). An innocent person, however, will be confused and baffled as they will have no idea what evidence could possibility implicate them. This sets the stage for a splitting attack which helps to determine truthfulness of a given individual.

Linguistics
Analysing which word can be a boomerang word depends on the word's exclusivity to that person, how common that word is generally, and how unique the meaning is. For example, associating elephants with secret documents wouldn't be a common association. Associating paper with secret documents would be, and would fail.

The term boomerang comes from the fact the word returns - the guilty party usually repeats the word verbally. Similar to a lie tell, where it's believed liars repeat the question they're thrown to buy time to form a lie: 'Me, guilty? A murderer? Never'. In this case, it' exploits part of mirror neuron's tendency to 'mirror' back information (including words). Regardless if Gramps or Tom explicitly acknowledge, react or deny 'elephant', the fact they react at all is the verification needed, not the words they are saying.

Countermeasures
Boomerang words are difficult to counter because they are hard to spot. They can be any word, and it's key component relies on a reaction. The person throwing the boomerang word can be anyone, at any time, in any place (whether written or verbal). Boomerang words in person are almost impossible to evade because of subconscious reactions and dilation to pupils and micro-expressions will dictate the answer immediately, regardless of statement.

In writing, boomerang words are less effective depending on the speed of the writing delivery. The faster it is, the more likely a boomerang will succeed.

The only way to be sure a boomerang word fails, is to not react to anything that is trying to provoke a reaction, or utilise clearing the baffles if appropriate. Non-reactions might be suspicious themselves, especially if the absence is more suspicious than the reaction. The best safeguard to any boomerang word is to be truthful. That way no word is exclusive.