1550s, "net-like arrangement of threads, wires, etc., anything formed in the manner of or presenting the appearance of a net or netting," from net (n.) + work (n.). Extended sense of "any complex, interlocking system" is from 1839 (originally in reference to transport by rivers, canals, and railways). Meaning "broadcasting system of multiple transmitters" is from 1914; sense of "interconnected group of people" is by 1934 in psychology jargon.