We normally decide how to pronounce an unfamiliar word by drawing analogies with English words we already know. For example, we knew how to pronounce “-ly” from words like “slowly,” so it isn’t too hard to figure out how to pronounce “bigly.”
But sometimes this approach runs into problems. In this case, there just aren’t any common English words ending in -efe. A wild-card search on the very comprehensive dictionary aggregator OneLook yielded the following list of words: jefe, fefe, efe, hefe, okeefe, hogrefe, keefe, reprefe, tefe and kefe. Pretty obscurefe.
So we have to search further afield. Maybe we go for the Spanish word “jefe,” meaning “boss.” Maybe we look to a different vowel, as in “fife” or “cafe.” Maybe we look to other spellings of the /f/ sound at the end of a word, like “ff” as in “fluff,” “gaffe” and “coiffe.”
The problem is that none of these is a close analogue, making it unsurprising that several Twitter polls have found that people are strongly split. But it looks like the lack of -fefe endings won’t remain true for long. People have started smashing covfefe together with other words to refer to the covfefe meme. There now exists the “threadfefe” (a thread about covfefe), an “exorfefe” (an exorcist of the word covfefe), a “presifefe” (president) and the slogan “If u think you’re above covfefe you’re part of the probfefe.”
It’s easy to find words that distinguish between other voiced/voiceless pairs in English - bus and buzz, fine and vine - but the two sounds represented by the “th” sequence in English are rarer and harder to learn, especially since English uses the same spelling for both of them.
A lot of people give up and just use near-minimal pairs like “think” and “this”, or “theta” and “they”, but there are actually a few true minimal pairs that you can use:
thigh - thy ether - either thistle - this’ll
It’s worth noting that function words in English, like pronouns, prepositions, and determiners, tend to have ð, while content words, especially nouns, tend to have θ.
Theta θ and eth ð are also found in the following noun/verb minimal pairs, at least for many dialects:
wreath - wreathe
(I put a wreath on the door / I wreathe the door)
teeth - teethe
(my teeth / the baby is teething)
loath - loathe
(I’m loath to do it / I loathe doing it)
sheath - sheathe
(in a sheath / to sheathe one’s sword)
sooth - soothe
(for sooth! / to soothe someone)
Here the vowels differ, but the theta θ to eth ð, noun to verb relationship is preserved:
cloth - clothe
(wear cloth / clothe oneself)
bath - bathe
(take a bath / bathe the baby)
breath - breathe
(take a breath / breathe deeply)
Make sure to try them at full volume, not whispering, because whispering involves turning off your vocal cords (which is why you can whisper when they’re inflamed with laryngitis).