agreeing in stupidity; displaying ignorance or foolishness by all ...1656
from Latin ūnus (one) + asinus (ass), after unanimous
FIRST DOCUMENTED USE
1656 - see EXAMPLE below
"...But I here dismiss you both together. So go your wayes (speaking to Doctor J. Wallis and Doctor S. Ward) you uncivil Ecclesiasticks, Inhumane Divines, Dedoctors of Morality, unasinous Collegues, Egregious pair of Isachar's, most wretched Vindices and Indices Academiarum; and remember Vespasians Law, &c..."
From: Elements of Philosophy the First Section, Concerning Body.. to which are added Six Lessons to the Professors of Mathematicks of the Institution of Sr. Henry Savile, in the University of Oxford
- Thomas Hobbes