Mid 17th century; earliest use found in John Gaule (1603/4–1687), Church of England clergyman and author. From post-classical Latin synergisticus + -al; compare -ical.
Definition of synergistical in US English:
synergistical
adjectiveˌsɪnəˈdʒɪstɪkl
Synergistic.
Origin
Mid 17th century; earliest use found in John Gaule (1603/4–1687), Church of England clergyman and author. From post-classical Latin synergisticus + -al; compare -ical.