"of the nature of a pivot," 1844, in the figurative sense, from pivot (n.) in the sense of "that upon which something turns or depends" + -al (1).
Entries linking to pivotal
pivot n.
"pin on which a wheel or other object turns," 1610s, from French pivot, from Old French pivot "hinge pin, pivot" (12c.), also "penis," a word of uncertain origin. Pevetsheres, evidently some kind of shears, is mentioned in a will registered in York in 1398. Figurative sense of "turning point, that on which some matter hinges or depends" is recorded from 1813.
-al 1
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)).