synonym (n.) Look up synonym at Dictionary.com
early 15c. (but rare before 18c.), from Latin synonymum, from Greek synonymon "word having the same sense as another," noun use of neuter of synonymos "having the same name as, synonymous," from syn- "together, same" (see syn-) + onyma, Aeolic dialectal form of onoma "name" (see name (n.)).