Nexus is all about connections. The word comes from nectere, a Latin verb meaning "to bind." A number of other English words are related to nectere. The most obvious is connect, but annex (meaning "to attach as an addition," or more specifically "to incorporate into a political domain") is related as well. When nexus came into English in the 17th century, it meant "connection." Eventually, it took on the additional meaning "connected series" (as in "a nexus of relationships"). In the past few decades it has taken a third meaning: "center" (as in "the trade nexus of the region"), perhaps from the notion that a point in the center of an arrangement serves to join together the objects that surround it.