The phrase "not least because" seems to be everywhere in journalism and other writing, often as an understated negation meaning, in large part because.

Individual publications, and even some publishers, lack the resources to mount an all-out arms race against ad blockers, not least because they’re unlikely to attract engineering talent when there are so many startups and established tech companies plying potential hires with equity—or at least free meals.

MacMillan provides a phrase definition of not least:

used for emphasizing the importance of a particular aspect of a situation

I at first assumed based on an Ngram search that the phrase was a recent one, but I found one use from 1897:

The figures given above must be highly gratifying to the examining bodies, not least because they show that the present stage of musical education warrants further demands upon those who aspire to authoritative recognition.

That use seems casual and idiomatic, so I assume the phrase must go back even further than that.


  • Would this construction qualify as a set phrase?

  • Did this phrase exist significantly earlier than the turn of the century?

  • 1
    Here's a guess: The origin is the phrase "last, but not least, because" (in which "because" is not actually part of the set phrase--it could be "last, but not least, owing to" . . .
    – Xanne
    Commented Jul 14, 2017 at 5:08
  • Also it doesn't mean "in large part because." It means that this is one of the reasons, and not the least important one. But it's a hedge: there may be other important reasons.
    – Xanne
    Commented Jul 14, 2017 at 5:19
  • @Xanne I think you're onto something with the "last but not least" theory. And you make a valid point about the meaning, though I think it means more than just "not the least important reason." It usually seems to be a deliberate understatement, as the MacMillan definition appears to suggest. Commented Jul 14, 2017 at 5:44
  • "Last but not least" the shoemaker said--but thanks for a good question. :)
    – Xanne
    Commented Jul 14, 2017 at 5:50
  • The set idiomatic phrase is "not least", 'because' often follows the expression as it is generally used to explain why you are saying "not least". "Not least" might derive from "last but not least" where "not least" conveys the same meaning. The usage of "not least" as a stand alone expression appears to be from early 19th century - books.google.com/ngrams/…
    – user66974
    Commented Jul 14, 2017 at 10:09

2 Answers 2


The complete phrase 'not least because' appears at least as early as 1801.

Much are we disposed to view it with complacency, on account of the subject, and as the first production occasioned by the memorable event, and last, though not least, because it is the effort of a female pen; ....

The British Critic, v 17-18, 1801, p 518.

I did not find the phrase significantly earlier than the turn of the 18th century. Notably, it was there part of the variable 'last not least' idiomatic phrase, which is considerably older — from before 1595; an attestation from 1536 in an 1888 publication,

...and last, not least, the very lamentable death of the good queen (Katharine), ....

Calendar of letters, despatches, and state papers, ... v.5 pt.2 1536-1538,

may have been, but is not likely to have been, the product of a heavy editorial pen.

Whether or not 'not least because' qualifies as a set phrase depends on the definition of 'set phrase' intended. See the ELU question "Is 'set phrase' a set phrase?" for some definitions of 'set phrase'. The now defunct Freebase noted succinctly and accurately that "There is no clear dividing line between a commonly used phrase and a set phrase."


"not least because" OED (advanced search)

Here are the only seven entries that an OED advanced search provides--I have not followed up on the sources. This list demonstrates that the phrase has been around for a while but isn't a set piece, and in none of these quotations does it occur with "last but".

  1. stick, v.1 View full entry eOE ...they have just to stick it out — not least because of fears that anti-sickness ...

  2. matter, n.1 View full entry ?c1225 ... far more expensive full page, not least because it is set into news matter....

  3. usage, n. View full entry c1325 ...bar during normal usage hours, not least because it will shield off some of t...

  4. shopping, n.2 View full entry 1757 ...will never find a lower price, not least because it is commercially convenien...

  5. Motswana, n. and adj. View full entry 1830 ...e for the individual Motswana, not least because of privileged access to the ...

  6. clocking, n.2 View full entry 1872 ...mes rather an unreliable guide— not least because ‘clocking ’..is a far too common...

  7. octet, n. View full entry 1879 ...e by Hausmusik is fascinating, not least because it is the first time I have ...

  • This is a good collection of uses, but I don't think it proves that "the phrase has been around for quite a while." The dates in your list appear to be the earliest dates of each word, not each quote. Commented Jul 14, 2017 at 9:32
  • I think you're right. So it's just a starting point.
    – Xanne
    Commented Jul 14, 2017 at 16:19

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