This definition is included here in relation to link and interaction. First the etymology:

Early 15c., “a knot or lump,” from Latin nodus “knot” (see net (n.)). Originally borrowed c. 1400 in Latin form, meaning “lump in the flesh.”
Meaning “point of intersection” (originally of planetary orbits with the ecliptic) first recorded 1660s.

From computer science: A node is a basic unit used in computer science. Nodes are devices or data points on a larger network.