Nexus comes directly from Latin nexus, a noun meaning binding or tying together, from the verb nectere (to bind, tie). The Proto-Indo-European root *ned- (to bind) produced this Latin verb, which in turn generated a family of English words all concerned with connection: connect (to bind together), annex (to bind to), and nexus itself.
In Latin, nexus had both physical and legal meanings. Physically, it described any binding or fastening. Legally, nexus designated the binding obligation between debtor and creditor — in early Roman law, a nexus was a person who had been bound into service to repay a debt, effectively an indentured servant. This legal usage persisted in Roman jurisprudence and influenced later European legal vocabulary
English borrowed nexus in the 17th century as a learned term, initially used in philosophical and scientific writing to describe the connection between causes and effects or between elements of a system. The word carried connotations of centrality and convergence — a nexus was not just any connection but a focal point where multiple connections meet.
In modern usage, nexus appears frequently in three contexts. In legal and regulatory language, nexus describes the sufficient connection between a taxing authority and a person or entity — tax nexus determines whether a state can tax a business, for example. In academic and policy discourse, nexus describes the intersection of related systems — the water-energy-food nexus, the crime-poverty nexus. In technology, nexus has been adopted as a brand name by Google (Nexus phones and tablets) and by the Nexus system of pre-approved border crossing between the United
Science fiction has embraced nexus for its connotations of convergence and interconnection. The replicant-detecting Nexus models in Blade Runner and the Nexus of All Realities in Marvel Comics both draw on the word's suggestion of a point where multiple realities or connections converge.
The PIE root *ned- (to bind) had a more modest but related descendant in the Germanic languages: the English word net, from Old English nett, describing the bound or knotted mesh used for fishing and trapping. Nexus and net are thus distant cousins — both ultimately describing things that are tied together.