two

two recorded from Old English (in form twā) and of Germanic origin, the word comes ultimately from an Indo-European root shared by Latin and Greek duo.
if two ride on a horse, one must ride behind proverbial saying, late 16th century; meaning that of two people engaged on the same task, one must take a subordinate role.
it takes two to make a bargain proverbial saying, late 16th century, often used to imply that both parties must be prepared to give some ground. (Compare it takes two to tango below.)
it takes two to make a quarrel proverbial saying, early 18th century, meaning that some responsibility for a disagreement rests with each party to it.
it takes two to tango proverbial saying, mid 20th century, meaning that a cooperative venture requires a contribution from both participants.
there are two sides to every question proverbial saying, early 19th century, meaning that a problem can be seen from more than one angle. In classical Greek, Diogenes Laertius records of the Greek sophist Protagoras (b. c.485 bc) that, ‘Protagoras was the first to say that there are two sides to every question, one opposed to the other.’
two blacks don't make a white proverbial saying, early 18th century, meaning that one injury or instance of wrongdoing does not justify another. (Compare two wrongs don't make a right.)
two cultures literature and science as disciplines that tend to be mutually incompatible or hostile; the term was coined by the novelist and scientist C. P. Snow (1905–80) in ‘The two cultures and the scientific revolution’, title of The Rede Lecture given at Cambridge in 1959.
two heads are better than one proverbial saying, late 14th century, meaning that it is advisable to discuss a problem with another person. (Compare four eyes see more than two.)
two is company, but three is none proverbial saying, early 18th century; often used with the alternative ending ‘three's a crowd.’
two-minute silence observed on the anniversary of Armistice Day (11 November 1918), or on Remembrance Sunday; The Times of 12 November 1919 recorded that ‘At 11 o'clock yesterday morning the nation, in response to the King's invitation, paid homage to the Glorious Dead by keeping a two minutes' silence.’ (Later sources refer to a silence of two minutes' duration having been observed by Canadian railways and churches in memory of those Canadians who drowned in the Titanic disaster of 1912, but contemporary use of the phrase is not recorded.)
two nations the rich and poor members of a society seen as effectively divided into separate nations by the presence or absence of wealth; the phrase comes from Disraeli's novel Sybil (1845), and has given rise to the expression One Nation.
two of a trade never agree proverbial saying, early 17th century; meaning that close association with someone makes disagreement over policy and principles more likely.
Two Sicilies the former kingdom of Naples and Sicily. Originally a single state uniting the southern peninsula of Italy with Sicily, it was divided in the 13th century between the Angevin dynasty on the mainland territory and the Aragonese dynasty on the island; both claimed title to the kingdom of Sicily. In the mid 15th century the state was reunited under Alfonso V of Aragon, who took the title ‘rex Utriusque Siciliae [king of the Two Sicilies]’.
two wrongs don't make a right proverbial saying, late 18th century, meaning that a first injury does not justify a second in retaliation. (Compare two blacks don't make a white.)
while two dogs are fighting for a bone, a third runs away with it proverbial saying, late 14th century, meaning that while the attention of the disputants is on their quarrel, both may lose possession of what they are fighting over to a third party.

See also between two stools one falls to the ground, a bird in the hand is worth two in the bush, two boys are half a boy, kill two birds with one stone, no man can serve two masters, one for sorrow, two for mirth.