"having two heads," 1640s, from Latin biceps (genitive bicipitis; see biceps) + -al (1).
Entries linking to bicipital
biceps
1630s (adj.) "two-headed," specifically in anatomy, "having two distinct origins," from Latin biceps "having two parts," literally "two-headed," from bis "double" (see bis-) + -ceps, combining form of caput "head" (from PIE root *kaput- "head"). As a noun meaning "biceps muscle of the arm," from 1640s, so called for its structure. Despite the -s, it is singular, and classicists insist there is no such word as bicep.
-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)).