The compound 'three-person' is a modern English formation following the common pattern of combining a number with a noun to create a descriptive adjective. The root for 'three' is ancient, tracing back to the Proto-Indo-European trei-, which denoted the cardinal number and is the ancestor of similar terms across many Indo-European languages. 'Person' has a more complex semantic journey, originating from the Latin persona, which referred to a theatrical mask and, by extension, a role or character played, eventually broadening to mean an individual human. The logic of the compound is transparently arithmetic, directly combining the concept of the quantity 'three' with the entity 'person' to specify a group or unit composed of exactly three individuals.

Structure: three (number) + person (human being) - three: From Old English þrīe, þrēo, of Germanic origin; related to Dutch drie and German drei, from an Indo-European root shared by Latin tres and Greek treis. Functions as a numerical quantifier. - person: From Old French persone, from Latin persona 'actor's mask, character in a play', later 'human being'. Functions as the noun being quantified.