diagonal

Where does the word "diagonal" come from? It comes from Greek diagonios, and was adopted directly into English (1500s).

Diagonal’s story begins in Greek: diagonios meant “through the angles.” Literally through the angles, from dia (through) and gonia (angle). It reached English by 1500s as diagonal. Settled as the geometric word for a line connecting two non-adjacent corners. Today, diagonal means a straight line connecting two non-adjacent corners of a shape.

1. Stage 1 · Greek · ancient diagonios "through the angles", literally through the angles, from dia (through) and gonia (angle).
2. Stage 2 · English · 1500s diagonal "a line connecting two non-adjacent corners of a shape", settled as the geometric word for a line connecting two non-adjacent corners.