clarion

The noun is derived from Middle English clarion, clarioun (“trumpet with a narrow tube and a shrill sound, clarion; clarion player”) [and other forms], from Old French claron, clarïon (“clarion”) [and other forms], from Medieval Latin clāriōn, clario, clārōn (“clarion; trumpet”), from Latin clārus (“audible; clear, distinct, loud; (visually) bright, clear”), ultimately from Proto-Indo-European *kelh₁- (“to call, summon; to cry”).

The adjective is from an attributive use of the noun.

From Middle English clariounen (“of a horn or trumpet: to blow, sound”), from clarioun (noun) (see etymology 1) + -en (suffix forming the infinitives of verbs). Later uses may also be derived directly from the noun.