A shibboleth (/ˈʃɪbəlɛθ/^[1] or /ˈʃɪbələθ/^[2]) is a word or custom whose variations in pronunciation or style can be used to differentiate members of ingroups from those of outgroups. Within the mindset of the ingroup, a connotation or value judgment of correct/incorrect or superior/inferior can be ascribed to the two variants.

The term originates from the Hebrew word shibbólet (שִׁבֹּלֶת), which literally means the part of a plant containing grains, such as an ear of corn or a stalk of grain^[3] or, in different contexts, "stream, torrent".^[4][5] The modern use derives from an account in the Hebrew Bible, in which pronunciation of this word was used to distinguish Ephraimites, whose dialect lacked a /ʃ/ phoneme (as in shoe), from Gileadites, whose dialect did include such a phoneme.

Recorded in the Book of Judges, chapter 12, after the inhabitants of Gilead inflicted a military defeat upon the tribe of Ephraim (around 1370–1070 BC), the surviving Ephraimites tried to cross the Jordan River back into their home territory and the Gileadites secured the river's fords to stop them. In order to identify and kill these refugees, the Gileadites put each refugee to say the word shibboleth. The Ephramite dialect did not contain the "sh" sound and so those who pronounced the word as sibboleth were identified as Ephramites and killed. ^[6][7]

In numerous cases of conflict between groups speaking different languages or dialects, one side used shibboleths in a way similar to the above-mentioned Biblical use, i.e., to discover hiding members of the opposing group. Modern researchers use the term "shibboleth" for all such uses, whether or not the people involved were using it themselves.

Today, in American English, a shibboleth also has a wider meaning, referring to any "in-group" word or phrase that can be used to distinguish members of a group from outsiders – even when not used by a hostile other group. The word is less well recognized in British English and possibly some other English-speaking groups. It is also sometimes used in a broader sense to mean jargon, the proper use of which identifies speakers as members of a particular group or subculture.

The term shibboleth can also be extended, as in the discipline of semiotics, to describe non-linguistic elements of culture such as diet, fashion and cultural values.

Cultural touchstones and shared experience can also be shibboleths of a sort. For example, people about the same age who are from the same nation tend to have the same memories of popular songs, television shows, and events from their formative years.One-hit wonders prove particularly effective. Much the same is true of alumni of a particular school, veterans of military service, and other groups. Discussing such memories is a common way of bonding. In-jokes can be a similar type of shared-experience shibboleth.

Yet another more pejorative usage involves underlining the fact that the original meaning of a symbol has in effect been lost and that the symbol now serves merely to identify allegiance, being described as nothing more than a "shibboleth".

Nobel Prize-laureate economist Paul Samuelson applied the term "shibboleth" in works including Foundations of Economic Analysis to an idea for which "the means becomes the end, and the letter of the law takes precedence over the spirit."^[8] Samuelson admitted that "shibboleth" is an imperfect term for this phenomenon, and sometimes used "fetish" as a synonym, though he complained that the latter "has too pejorative a ring."^[9]

Shibboleths have been used by different subcultures throughout the world at different times. Regional differences, level of expertise, and computer coding techniques are several forms that shibboleths have taken.

The legend goes that before the Guldensporenslag (Battle of the Golden Spurs) in May 1302, the Flemish slaughtered every Frenchman they could find in the city of Bruges, an act known as the Brugse Metten.^[10] They identified Frenchmen based on their inability to pronounce the Flemish phraseschilt ende vriend (shield and friend), or possibly 's Gilden vriend (friend of the Guilds). However, many Medieval Flemish dialects did not contain the cluster sch- either (even today's Kortrijk dialect has sk-), and Medieval French rolled the r just as Flemish did.^[11]

Bûter, brea, en griene tsiis; wa't dat net sizze kin, is gijn oprjochte Fries ( example (help·info)) means "Butter, rye bread and green cheese, whoever cannot say that is not a genuine Frisian" was used by the Frisian Pier Gerlofs Donia during a Frisian rebellion(1515–1523). Ships whose crew could not pronounce this properly were usually plundered and soldiers who could not were beheaded by Donia himself.^[12]

The Dutch used the name of the seaside town of Scheveningen as a shibboleth to tell Germans from the Dutch ("Sch" in Dutch is analyzed as the letter "s" and the digraph "ch", producing the consonant cluster [sx], while in German it is analyzed as the trigraph"sch," pronounced [ʃ]).^[13][14]

In October 1937 the Spanish word for parsley, perejil, was used as a shibboleth to identify Haitian immigrants living along the border in the Dominican Republic. The president of the Dominican Republic, Rafael Trujillo, ordered the execution of these people. It is alleged that between 20,000 and 30,000 individuals were murdered within a few days in the Parsley Massacre although more recent scholarship and the lack of evidence such as mass graves puts the actual total as low as 1000.^[15]

The Finnish army frequently used words containing -y, -ä and the diphthongs -yä or -yö because of their alienity to native Russian speakers.^{[citation needed]}

During World War II, some United States soldiers in the Pacific theater used the word lollapalooza as a shibboleth to challenge unidentified persons, on the premise that Japanese people often pronounce the letter L as R or confuse Rs with Ls; the word is also an American colloquialism that even a foreign person fairly well-versed in American English would probably mispronounce or be unfamiliar with.^[16] In George Stimpson's A Book about a Thousand Things, the author notes that, in the war, Japanese spies would often approach checkpoints posing as American or Filipino military personnel. A shibboleth such as "lollapalooza" would be used by the sentry, who, if the first two syllables come back as rorra, would "open fire without waiting to hear the remainder".^[17]

The BBC reportedly started using regional accents during WW2 on the wireless on the basis that Germans would find it harder to accurately mimic a regional accent, so would be identified should they manage to take over radio broadcasting and feed false wireless news to the population of the United Kingdom.

During The Troubles in Northern Ireland, use of the name Derry or Londonderry for the province's second-largest city was often taken as an indication of the speaker's political stance, and as such frequently implied more than simply naming a location.^[18]

In an episode of The West Wing titled "Shibboleth", President Bartlet becomes certain that a group of Chinese asylum seekers are indeed Christians in faith, when their representative uses the word shibboleth during their meeting.^[19]