maniacal (adj.)

c. 1600,  "affected with mania, raving with madness," from French maniaque (14c.), from Late Latin maniacus, from Greek maniakos, from mania (see mania). Borrowed at first in French form. From 1727 as "pertaining to mania." The noun, "one who is affected with mania, a madman," is attested by 1763, from the adjective.

suffix forming adjectives from nouns or other adjectives, "of, like, related to, pertaining to," Middle English -al, -el, from French or directly from Latin -alis (see -al (2)).