Definition
1. (verb) To confine or restrict a person — typically an enemy alien, prisoner of war, or political detainee — within a defined territory or facility during wartime or national emergency, without necessarily subjecting them to criminal prosecution. The confining authority exercises custodial control over the interned person's movement, though the degree of restriction varies from house arrest within a city to formal detention in a camp or fortress.
2. (noun, international law) A person subject to such confinement; one who has been interned.
3. (noun, employment/labor) In modern colloquial and increasingly legal usage, a person — typically a student or recent graduate — who works for an employer for a fixed period, often at reduced or no wages, for the purpose of gaining professional experience. This sense carries growing legal significance in employment and labor law, particularly regarding wage-and-hour obligations, but it is not the term's historical legal meaning.
Common Language
Modern common usage (Wiktionary): "A person who is interned, forcibly or voluntarily."
Historical common usage (Webster's 1913): Webster's 1913 marks the adjectival form "internal" as obsolete under this root, reflecting that the verb "to intern" had not yet fully naturalized into common English usage at that date.
The gap here is directional: ordinary modern English has largely absorbed the employment-trainee sense of "intern," while the legal sources treat the term almost exclusively in its wartime-detention and international-law sense. A researcher encountering "intern" in a contemporary employment dispute and a researcher encountering it in a World War II-era administrative law case are working with meanings that share a word but not a legal framework.
Common Confusion
The employment-trainee sense of "intern" (sense 3 above) now dominates popular usage and appears with increasing frequency in regulatory guidance, agency opinion letters, and litigation — but carries none of the international-law or detention-law infrastructure that the historical sources describe. Conflating these meanings causes real research errors: an index entry for "intern" in a pre-1950 legal source almost certainly refers to wartime or political confinement, not to unpaid labor. The reverse is equally true: modern employment-law materials discussing "intern" status draw on FLSA doctrine, not the law of armed conflict.
Why It Matters in Research
Corpus researchers face a clean chronological divide. In Law Mind sources predating the mid-twentieth century, "intern" and "internment" refer almost exclusively to the detention function in international and wartime law — the obligation of neutral states to confine belligerent forces entering their territory, and the authority of belligerents to detain enemy nationals. The detention-of-enemy-aliens cases and the World War II Japanese American internment administrative record sit within this framework.
The employment-trainee meaning accelerates in legal significance after the 1970s and becomes heavily litigated after the Department of Labor's six-factor test for unpaid internships (developed in the 2000s and revised circa 2018 using a "primary beneficiary" standard). Neither framework appears in the other's sources. A full-text search on "intern" across a mixed-era corpus will return false hits in both directions unless the researcher filters by date and subject-matter context.
Jurisdictional variation matters most in the employment sense: several states (California, New York) have extended wage-and-hour protections to interns beyond federal minimums, and state human rights laws may apply anti-discrimination protections to interns that federal law has not clearly extended.
The Bouvier entry is the most substantive of the historical sources and draws the international-law duty of neutrals into relief: a neutral state's obligation to intern — rather than release or allow continued military operation of — belligerent warships or troops. This is a specific, technical duty in the law of neutrality that researchers in international law history will need to trace through the laws of war literature, not through employment-law sources.
Historical Dictionary Support
All four historical dictionaries agree on the core definition: to restrict a person within a limited territory, typically in a political or wartime context. Anderson adds the illustrative specificity of "within a city or upon an island," which helpfully captures the graduated nature of internment — it need not mean a prison camp; it may mean geographical confinement with relative freedom of movement within that zone.
Bouvier is alone among the shelf sources in developing the international-law dimension, specifically the duty of neutral states respecting belligerent warships and troops. This is the entry's most practically useful content for legal historians and international-law researchers, and it points toward a body of customary international law and treaty law (Hague Convention materials, laws of war) that the dictionary itself does not cite by name.
None of the historical sources anticipate the employment-trainee meaning. This is not a gap in their scholarship; it reflects that the term had not yet acquired that meaning as a legal term of art. Researchers should not read the historical silence as authority for or against any position in modern intern-employment litigation.
Jurisdictional Note
In employment law, the legal status of unpaid interns — and employers' obligations toward them — varies significantly between federal law and state law. Federal courts apply a "primary beneficiary" test derived from FLSA doctrine; California and New York impose additional or broader protections under state wage-and-hour statutes. In international law, the internment duty of neutral states is governed by treaty and customary international law rather than domestic statute.