Needs must means necessity leaves you no choice. The full saying is needs must when the devil drives, a shortening of a proverb printed in 1498 as he must nedys go that the deuell dryues. It is usually said with a shrug, about something done unwillingly because there is no way round it.
What’s the origin of the phrase ‘Needs must’?
The phrase is old. In earlier texts it is almost always given in its fuller form - needs must when the devil drives. that is, if the devil is driving you, you have no choice. This dates back to Early Modern English texts, for example Assembly of Gods, circa 1500:
“He must nedys go that the deuell dryues.”
The poem does not present that line as its own invention. It introduces it as something people were already saying, in the line immediately before: “For hit ys oft seyde by hem that yet lyues”, that is, it is often said by those still living. Oscar Lovell Triggs, who edited the poem in 1895, records that the earliest surviving print of it is a Wynkyn de Worde folio dated 1498.
John Heywood printed the proverb in his collection of English proverbs of 1546, in this form:
“And that he must needes goe whom the divell doth drive.”
Shakespeare used the phrase several times; for example, in All’s Well That Ends Well, 1601:
Countess: Tell me thy reason why thou wilt marry.
Clown: My poor body, madam, requires it: I am driven on by the flesh; and he must needs go that the devil drives.
The Folger Shakespeare edition places that exchange in Act 1, Scene 3. Shakespeare’s clown says must needs where the modern saying says needs must, and both orders work because needs here is not the plural noun. It is an old adverb meaning “of necessity, necessarily”, which Etymonline dates to the late 14th century and describes as surviving in archaic constructions involving must. So needs must amounts to “of necessity, one must”.
The phrase became pared down to needs must by the end of the 19th century and, even in that short form, it is rather archaic-sounding and is fading from popular use. This despite a high-profile appearance on TV in Blackadder II, 1985:
“Needs must when the devil vomits into your kettle.”
The two-word form was already in print by 1895. In Marie Corelli’s novel The Sorrows of Satan, 1895, a character quotes the whole proverb as an old maxim and, in the same sentence, uses the first two words on their own: “I always realize the ‘needs must’ of things”.