1796, from symmetry + -ic. Earlier in the same sense was symmetral (1650s).
Entries linking to symmetric
symmetry n.
1560s, "relation of parts, proportion," from French symmétrie (16c.) and directly from Latin symmetria, from Greek symmetria "agreement in dimensions, due proportion, arrangement," from symmetros "having a common measure, even, proportionate," from assimilated form of syn- "together" (see syn-) + metron "measure" (from PIE root *me- (2) "to measure"). Meaning "harmonic arrangement of parts" first recorded 1590s.
-ic
Middle English -ik, -ick, word-forming element making adjectives, "having to do with, having the nature of, being, made of, caused by, similar to," from French -ique and directly from Latin -icus or from cognate Greek -ikos "in the manner of; pertaining to." From PIE adjective suffix *-(i)ko, which also yielded Slavic -isku, adjectival suffix indicating origin, the source of the -sky (Russian -skii) in many surnames. In chemistry, indicating a higher valence than names in -ous (first in benzoic, 1791).
In Middle English and after often spelled -ick, -ike, -ique. Variant forms in -ick (critick, ethick) were common in early Modern English and survived in English dictionaries into early 19c. This spelling was supported by Johnson but opposed by Webster, who prevailed.