"religious song," c. 1000, from Old French ymne and Old English ymen, both from Late Latin hymnus "song of praise," from Greek hymnos "festive song or ode in praise of gods or heroes" (also sometimes of mournful songs), used in Septuagint to translate several Hebrew words meaning "song praising God." Possibly a variant of hymenaios "wedding song," from Hymen, Greek god of marriage, or, as per Watkins, from a PIE root *sam- "to sing" (source also of Hittite išhamai "he sings," Sanskrit saman- "hymn, song"). Evidence for the silent -n- dates from at least 1530.
-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.