Where I saw or heard the word: reading a Newsweek article.
Perfervid
per·fer·vid /pərˈfɜrvɪd/ Pronunciation Key - Show Spelled Pronunciation[per-fur-vid] -adjective very fervent; extremely ardent; impassioned: perfervid patriotism.
[Origin: 1855–60; < NL perfervidus. See per-, fervid]
—Related formsper·fer·vid·i·ty, per·fer·vid·ness, noun
per·fer·vid·ly, adverb
per·fer·vor; especially British, per·fer·vour, noun
Will I use it? No.
Reason: It sounds ugly.