Ef

“Now ef ye alls don’t quit fussin’, I’ll set the boogers arter ye ter-night,” which was a dire and telling threat, for, to the mountain children, “boogers” meant ghosts, witches, hobgoblins, thieves, or any other terrible, mysterious creature of the night.

Ef was probably a bilabial, not a labiodental spirant, as is also evident from Goth.

I have drunk en-ee-cee-tee-ay-ar from the ef-ell-oh-doubleyou-ee-ar-ess in his gee-ay-ar-dee-ee-en many a time.

Captain Tom would have hired him to hunt down his own child, ef Rosebud hadn’t interfered.

Under certain conditions, the localized EF near an energized transmission line conductor can produce small electric discharges, ionizing nearby air. […] Modern “bipolar” cardiac devices are much less susceptible to interactions with EFs. Manufacturers of pacemakers and other IMDs have indicated that EFs below 6 kV/m are unlikely to cause interactions affecting the operation of most of their devices.