Etymology
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je ne sais quoi (n.)

"an inexpressible something," French, literally "I do not know what."

[T]hey are troubled with the je-ne-scay-quoy, that faign themselves sick out of niceness but know not where their own grief lies, or what ayls them. [Thomas Blount, "Glossographia," 1656]
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absit omen (interj.)
Latin, literally "may this omen be absent." Added to an expression of something one does not wish to be true or come true, "may it not be ominous;" from third person singular present subjunctive of abesse "be away" (see absent (adj.)) + omen (see omen).
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fieri facias (n.)
writ concerning a sum awarded in judgment (often requiring seizure and sale of property for debt), Latin, literally "cause it to be done, cause to be made," the first words of the writ, from Latin fieri "to be made, come into being" (see fiat). Second word from facere "to do" (from PIE root *dhe- "to set, put").
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go for (v.)
1550s, "be taken or regarded as," also "be in favor of," from go (v.) + for (adv.). Meaning "attack, assail" is from 1880. Go for broke is from 1951, American English colloquial.
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nolle prosequi 

in law, formal notice to a plaintiff that the prosecutor will not continue a suit, Latin, literally "to be unwilling to pursue." The derived verb nolle-pross "to abandon (a prosecution, etc.) by nolle prosequi" is attested from 1880. Latin nolle "be unwilling" is from ne "not" + velle "will."

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go west (v.)
19c. British idiom for "die, be killed" (popularized during World War I), "probably from thieves' slang, wherein to go west meant to go to Tyburn, hence to be hanged, though the phrase has indubitably been influenced by the setting of the sun in the west" [Partridge]. Compare go south.
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comme il faut 

"according to etiquette," 1756, French, literally "as it should be." From comme "as, like, how," from Old French com, from Vulgar Latin *quomo, from Latin quomodo "how? in what way?," pronominal adverb of manner, related to quam "how much?," qui "who" (from PIE root *kwo-, stem of relative and interrogative pronouns). With il, from Latin ille "this" (see le) + faut, third person singular present indicative active of falloir "be necessary," literally "be wanting or lacking" (see fail (v.)).

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de minimis 
Latin, literally "of little things," thus, "so minor as to not be worth regarding."
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cogito ergo sum 

Latin phrase, literally "I think, therefore I am;" the starting point of Cartesian philosophy (see Cartesian), from cogito, first person singular present indicative active of cogitare "to think" (see cogitation) + ergo "therefore" (see ergo) + sum, first person singular present indicative of esse "to be" (from PIE root *es- "to be").

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go over (v.)
1580s, "review point by point;" see go (v.) + over (adv.). Meaning "be successful" is from 1923.
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