chord, cord. The Columbia Guide to Standard American English. 1993

Kenneth G. Wilson (1923–).  The Columbia Guide to Standard American English.  1993.

chord, cord (nn.)

There are really two words spelled chord. The musical chord is composed of three or more usually concordant notes sounded at the same time, and in mathematics, geometry, and engineering, a chord is a line that joins two points on a curve. The musical chord comes from accord; the math chord comes from Greek chorda, meaning “string or gut.” A cord is also a string, and some strings make music. So is it vocal chords or vocal cords, spinal cord or spinal chord? Both spellings are historically accurate, but today’s American English pretty much insists on vocal cord and spinal cord. Still, it is no wonder questions arise.	1
A cord of wood is a measure: a stack four by four by five feet; it was originally the amount that could be tied with a cord. Cord is also a fabric—corduroy is one such—in which the ribbed texture looks like cords.	2

The Columbia Guide to Standard American English. Copyright © 1993 Columbia University Press.