The word 'vas' entered English directly from Latin, where 'vās' (plural 'vāsa') broadly meant a container, vessel, or utensil. In its journey into specialized English medical and biological terminology, its meaning narrowed significantly from a general container to specifically denote a tubular vessel or duct within an organism that contains or conveys a fluid. This semantic shift reflects the tendency of scientific language to adopt and precisely redefine classical terms. The logic of its modern usage lies in viewing the anatomical duct as a specialized container for bodily fluids, preserving the core Latin concept of a vessel while applying it to a biological structure.

The word is a simplex loanword from Latin. It is a direct borrowing of the Latin noun 'vās', meaning 'vessel, dish, utensil'.