The term is a modern compound formation, directly descriptive of the game's format. It combines the numeral "three," of ancient Proto-Indo-European origin (trei-), with the preposition "on," from Old English, to denote the number of participants actively engaged per side. The structure "X-on-X" is a productive pattern in English for naming competitive formats, creating a transparent and logical label that literally means "three players competing against three players." This compounding bypasses classical roots in favor of a straightforward, vernacular description of the sporting contest.

Structure: three + on + three - three: From Old English þrīe, þrēo, of Proto-Germanic origin; related to Latin trēs, Greek treis. Functions as a numeral. - on: From Old English on, of Germanic origin. Functions as a preposition indicating association or participation. - three: (As above) Functions as a numeral.