This inspired this question; I should verify whether the prefix really means something.

from Latin de- "away" + fallere "to deceive, to cheat; to put wrong, to lead astray, cause to be mistaken; to escape notice of, be concealed from" (see fail (v.))

The purpose of de- here is unclear to me, because the semantic notion of "away" does not appear in the verb *defallere and because Latin already had fallere. So why might this prefix have been added to this word prior to entering Old French?

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    I'm a little confused—I can't find defallere in any of the dictionaries I have at hand. (Though the OLD is not among them.) Feb 29, 2016 at 0:21
  • @JoelDerfner Sorry for any confusion; the Etymonline does list it with an asterisk (as indicated above) and so it may be attested, if not in Classical Latin, in Vulgar Latin? Wiktionary asserts it too, but Wiktionary can err.
    – user37
    Feb 29, 2016 at 1:42
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    Ah, okay, so listings of a word with an asterisk mean that it isn't actually attested. I'm not experienced enough in either Vulgar Latin or in lexicography to explain why the etymonline.com entry contains it, but if it's got an asterisk, we don't have an example of it. So it may be that those who spoke Latin saw the same redundancy you do! Feb 29, 2016 at 2:43
  • @Nathaniel I asked it because its derivatives exist in English (en.wiktionary.org/wiki/default#Etymology) and French; so it interests me. Does this clarify?
    – user37
    Feb 29, 2016 at 5:11
  • @JoelDerfner Thank you for your thoughts! I welcome your positive attitude!
    – user37
    Feb 29, 2016 at 5:12

1 Answer 1


The prefix de- does not necessarily mean "away." Etymology online says:

usually meaning "down, off, away, from among, down from," but also "down to the bottom, totally" hence "completely" (intensive or completive)

Note in particular the second portion of this. Thus, a possible explanation is that the de- was added to the Latin fallere as an intensifier, indicating complete deceit or failure. This doesn't explain why EO glosses de- as "away" in its explanation, but it's one way to explain the etymology.

The OED, in its discussion of the de- prefix in English, mentions several Latin words that had the prefix de- as an intensifier:

  • deplorare, to weep as lost
  • despoliare, to spoil utterly
  • declarare, to make quite clear

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