Derived from a Latin word meaning "hearth," focus now has a basic meaning of "gathering point," "center of attraction, attention,, or interest," "point of concentration": "Their home is the focus of community activity." "At the dance, she was the focus of everyone's interest." Nexus comes from a Latin word meaning "binding" and refers to a tie, a link, a means of connecting: "The nexus of this student body is school spirit." "Respect for everyone else is the nexus of civilized society." "Focus down on" is a wordy, trite phrase from which down should be dropped. See also center around.
Dictionary of problem words and expressions. Harry Shaw. 1975.