The word "confine" entered English in the 1520s from French confiner, which derived from the plural noun confins (borders, boundaries). The French word traced back to Latin confine, the neuter form of the adjective confinis (bordering upon, adjacent), built from con- (together, with) and finis (end, limit, boundary).
Latin finis is one of the most consequential words in the history of English vocabulary, yet its own etymology remains frustratingly opaque. It has no secure Proto-Indo-European derivation. Some scholars have tentatively connected it to figere (to fix, fasten), reasoning that a boundary is a fixed point, but this proposal has not achieved consensus. What is beyond dispute is the extraordinary productivity of finis in English: "finish," "final," "finite," "infinite," "define," "definite," "refine," "finance," and "fine" all descend from it.
The semantic development of "confine" in English follows an interesting trajectory. The noun — usually in the plural "confines" — appeared first, referring to boundaries or borders in a geographical sense. Shakespeare used it this way in Richard II: "This earth of majesty, this seat of Mars, / This other Eden, demi-paradise, / This fortress built by Nature for herself / Against infection and the hand of war." The verb followed, initially meaning to border upon (a territory confines another) before shifting to its dominant modern sense of restriction and imprisonment.
The relationship between boundaries and imprisonment is linguistically deep. "Define" literally means to set the limits of something. "Finite" means having an end. "Confine" intensifies the spatial metaphor — con- adds a sense of enclosure, of being bounded on all sides rather than merely having a single boundary. This semantic intensification explains why "confine" came to mean imprisonment rather than simply bordering.
In legal and medical English, "confinement" developed a euphemistic meaning that persisted for centuries: the period of a woman's lying-in before and after childbirth. This usage, now largely obsolete, reflected the practice of restricting a pregnant woman's movements and social activities in the weeks surrounding delivery. The euphemism softened the reality of what was, historically, a genuinely dangerous period of enforced rest.
Modern usage spans a wide range, from the literal (confining a prisoner to a cell) to the figurative (confining a discussion to relevant topics). The noun "confines" retains its original spatial sense more faithfully than the verb — we still speak of "the confines of a building" or "within the confines of the law," meaning within established boundaries rather than under imprisonment.