Idioms

    without fail, with certainty; positively: I will visit you tomorrow without fail.

Origin of fail

1175–1225; Middle English failen < Anglo-French, Old French faillir < Vulgar Latin *fallīre, for Latin fallere to disappoint, deceive
Related formsun·failed, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

British Dictionary definitions for unfailed

fail

1

verb

to be unsuccessful in an attempt (at something or to do something)
(intr) to stop operating or working properlythe steering failed suddenly
to judge or be judged as being below the officially accepted standard required for success in (a course, examination, etc)
(tr) to prove disappointing, undependable, or useless to (someone)
(tr) to neglect or be unable (to do something)
(intr) to prove partly or completely insufficient in quantity, duration, or extent
(intr) to weaken; fade away
(intr) to go bankrupt or become insolvent

noun

a failure to attain the required standard, as in an examination
without fail definitely; with certainty

Word Origin for fail

C13: from Old French faillir, ultimately from Latin fallere to disappoint; probably related to Greek phēlos deceitful

fail

2

noun

Scot a turf; sod

Word Origin for fail

perhaps from Scottish Gaelic fàl
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for unfailed

fail

v.

early 13c., from Old French falir (11c., Modern French faillir) "be lacking, miss, not succeed," from Vulgar Latin *fallire, from Latin fallere "to trip, cause to fall;" figuratively "to deceive, trick, dupe, cheat, elude; fail, be lacking or defective." Related: Failed; failing. Replaced Old English abreoðan.

fail

n.

late 13c. (e.g. without fail), from Old French faile "deficiency," from falir (see fail (v.)). The Anglo-French form of the verb, failer, also came to be used as a noun, hence failure.

Online Etymology Dictionary, © 2010 Douglas Harper

Idioms and Phrases with unfailed

fail

see without fail; words fail me.

The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.