OED to the rescue
Posted by R. Berg on February 26, 2002
In Reply to: Origin of - Needs must posted by Camel on February 26, 2002
: : : I have always found this a little confusing, especially when it's shortened just to 'needs must' because it makes it seem like 'needs' is a noun. I must go the verb below and 'needs' an unusual adverb or is 'must needs go' the verb?
: : : "He must needs go that the Devil drives." Shakespeare: All's Well That-Ends Well
: : : Any elucidation much appreciated.
: : Hmmm. I didn't know the phrase was of Shakespearean origin - or did Bill just use a phrase that was already current?
: : Today's more usual version is "needs must when the Devil drives"... I say "more usual", but it's hardly in common usage. Thanks is clearly owed to Shakespeare, because parsing the modern version of the phrase correctly would have been next to impossible.
: : My bet is that Camel's first instincts are right - "needs" is some archaic form of adverb, meaning "with necessity". This does seem fractionally tautologous in the line from "All's Well That Ends Well", but maybe the repetition is done for emphasis.
: : I'm probably entirely wrong on all this, but what the Heck?
: I think the phrase may be a proverb. I found it in Brewer's Dictionary of Phrase and Fable compiled by E. Cobham Brewer. It exists in in other languages too. The French, which you'll appreciate more than I, "Il faut marcher quand le diable est aux trousses;" and also in Italian "Bisogna andare, quando il diavolo è vella coda.", which, as a self-confessed linguist, I dare say you'd be able to appreciate without too much effort.
I have a friend who is a linguist, but he makes his graduate assistants do his confessing for him. Back to the issue at hand, though: The adverb faction is (Br.: "are") right.
OED has "need" as an obsolete adverb., defined as "Of necessity, necessarily, etc. (Usually with 'shall' or 'must': cf. NEEDS adv.)" Quotations begin at the year 893 (my keyboard doesn't have all the characters for the early ones) and end at 1732. 1631: "His good Horse Arundell, from whence the ancient Castel of that name, must neede be call'd so."
NEEDS as an adverb,
and not marked obsolete: "Of necessity, necessarily.
a. In general use. Now rare. . . .
b. In clauses containing 'must.' . . . 1470-85 MALORY 'Arthur' . . . Depe draughtes of deth toke her, that nedes she must dye. . . .
c. Directly following the vb., in 'must needs.' . . . 1529 WOLSEY . . . Thes thyngs consyderyd . . . must nedys make me yn agony. . . . 1822 IRVING . . . The Squire must needs have something of the old ceremonies observed on the occasion. . . .
d. So 'needs must.' Freq. as an elliptic phrase, esp. after 'than' or 'if.' . . . 1667 MILTON . . . Needs must the Power That made us . . . Be infinitly good. 1734 BERKELEY . . . I shall stay no longer in Dublin than needs must. . . . 1871 BROWNING . . . She shall go, if needs must."