formido.

The verb is probably derived from the noun. Their origin is unknown: * Possibly from the root Proto-Indo-European *dʰer- (“to hold”) (the same of firmus), as the fear that makes one rigid. * Alternatively cognate with Ancient Greek μόρμορος (mórmoros, “fear, panic”), μύρμος (múrmos, “fear”) and μορμώ (mormṓ, “bogey, she-monster”), with the same dissimilation *morm- > form- seen in formīca and possibly fōrma. If this is of Proto-Indo-European origin, it would appear to be a reduplication of a root *mer-, possibly the same root as *mer- (“to disturb”) and/or the source of *mor- (“incubus, mare (evil female spirit of nightmares)”) (which is otherwise thought to be from *mer- (“to disappear, die”)). However, De Vaan reconstructs only a stem *mormo- which he does not allow an etymology. If not Indo-European, then a substrate origin must be considered, which the variation of forms in Greek and morphological obscurity in both languages make likely. The suffix component -īd- is unexplained in either case, but compare -idus (with different vowel length), -īdō (in libīdō, cupīdō) and -ēdō (in more nouns).

The verb is probably derived from the noun. Their origin is unknown: * Possibly from the root Proto-Indo-European *dʰer- (“to hold”) (the same of firmus), as the fear that makes one rigid. * Alternatively cognate with Ancient Greek μόρμορος (mórmoros, “fear, panic”), μύρμος (múrmos, “fear”) and μορμώ (mormṓ, “bogey, she-monster”), with the same dissimilation *morm- > form- seen in formīca and possibly fōrma. If this is of Proto-Indo-European origin, it would appear to be a reduplication of a root *mer-, possibly the same root as *mer- (“to disturb”) and/or the source of *mor- (“incubus, mare (evil female spirit of nightmares)”) (which is otherwise thought to be from *mer- (“to disappear, die”)). However, De Vaan reconstructs only a stem *mormo- which he does not allow an etymology. If not Indo-European, then a substrate origin must be considered, which the variation of forms in Greek and morphological obscurity in both languages make likely. The suffix component -īd- is unexplained in either case, but compare -idus (with different vowel length), -īdō (in libīdō, cupīdō) and -ēdō (in more nouns).