a combination of -ic and -al1 , used in forming adjectives from nouns (rhetorical), providing synonyms to words ending in -ic, (poetical), and providing an adjective with additional meanings to those in the -ic, form (economical).
adjectival suffix, mostly the same as -ic but sometimes with specialized sense (e.g. historic/historical), Middle English, from Late Latin -icalis, from Latin -icus + -alis.