perfervid
Extremely, excessively, or feverishly passionate; zealous.
Manders — perfervid — 'hell'-ing excitedly (was there no one left on earth to convert but me?), quoting over a century from Marx and Nietzsche to Lenin, Lloyd George, and Eden, and on to Vessant and Mundaine and himself...
Where it comes from
From Late Latin perfervidus, from Latin per- + fervidus. By surface analysis, per- + fervid; compare pellucid.
Adapted from the Wiktionary entry perfervid (CC BY-SA 4.0).