also co-axial, "having a common axis," 1850 as a term in mathematics; the coaxial cable, one containing several coaxial lines, is attested by that name from 1934. See co- + axial. Earlier coaxal (1847). Related: Coaxially; coaxiation.
in Latin, the form of com- "together, with" in compounds with stems beginning in vowels, h-, and gn-; see com-. Taken in English from 17c. as a living prefix meaning "together, mutually, in common," and used promiscuously with native words (co-worker) and Latin-derived words not beginning with vowels (codependent), including some already having it (co-conspirator).