1715, from increment + -al (1). Related: Incrementally.
mid-15c., "act or process of increasing," from Latin incrementum "growth, increase; an addition," from stem of increscere "to grow in or upon" (see increase (v.)). Meaning "amount of increase" first attested 1630s.
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)).
updated on July 22, 2012