(n.) a poor comparison
A fomblitude is a poor comparison, or an example that doesn’t stand up to scrutiny.
That’s a word tagged as “obsolete” by the Oxford English Dictionary, which also lists just a single written record of it: in a famous Tudor-era polemic called A Defense of the Sincere and True Translations of the Holy Scriptures (1583), the sixteenth century Puritan scholar and theologian William Fulke used fomblitude to describe the inaccuracies he saw in the so-called Douay–Rheims Bible, a radical translation of the New Testament published in France the previous year. If the word fomblitude were Fulke’s and Fulke’s alone, that would make it a lovely example of a hapax legomenon—but in fact it seems to have survived for a time in spoken English, as it later found its way into a number of glossaries of dialectal and provincial English in the nineteenth century.
Etymologically, the –tude at the end of words like fomblitude and similitude will be a familiar root to English speakers, the origins of which lie in Latin. The suffix –tudo was employed in Latin to form nouns from adjectives and adverbs. So altus, meaning “high” (an adjective) in Latin, became altitudo, meaning “height” (a noun), and eventually gave us English speakers the word altitude.
The same goes for nouns like fortitude (from the Latin adjective fortis, “brave”), aptitude (from aptus, “appropriate, fitted”), multitude (from multus, “much”), hebetude (from hebus, “blunt”), solitude (from solus, alone), and both latitude (from latus, “broad”) and longitude (from longus, “long”). This setup became so familiar to English speakers, in fact, that we eventually began forming our own –tude words without the need of any Latin root at all, creating new (and often fairly clumsy) words like exactitude, decrepitude, impromptutude, plumpitude and correctitude.
Whether Fulke invented the word fomblitude himself is unclear, but it would fall in this second category: far from sandwiching together two formal Latin roots, its basis appears to have been the decidedly Anglo-Saxon verb fumble.