The word "twelve" is the largest number with a single-morpheme name in English. Etymology suggests that "twelve" (similar to "eleven") arises from the Germanic compound twalif "two-leftover", so a literal translation would yield "two remaining [after having ten taken]". This compound meaning may have been transparent to speakers of Old English, but the modern form "twelve" is quite opaque. Only the remaining tw- hints that twelve and two are related.
A group of twelve things is called a duodecad. The ordinal adjective is duodenary, twelfth. The adjective referring to a group consisting of twelve things is duodecuple.
The number twelve is often used as a sales unit in trade, and is often referred to as a dozen. Twelve dozen are known as a gross. (Note that there are thirteen items in a baker's dozen.). the expression "baker's dozen" dates to the 13th century in one of the earliest English statutes, instituted during the reign of Henry III (1216–1272), called the Assize of Bread and Ale. Bakers who were found to have shortchanged customers (some variations say that they would sell hollow bread) could be subject to severe punishment. To guard against the punishment of losing a hand to an axe, a baker would give 13 for the price of 12, to be certain of not being known as a cheat. Specifically, the practice of baking 13 items for an intended dozen was insurance against "short measure", on the basis that one of the 13 could be lost, eaten, burnt, or ruined in some way, leaving the baker with the original legal dozen. The practice can be seen in the guild codes of the Worshipful Company of Bakers in London.
Force 12 on the Beaufort wind force scale corresponds to the maximum wind speed of a hurricane. The duodenum (from Latin duodecim, "twelve") is the first part of the small intestine, that is about twelve inches (30 cm) long. More precisely, this section of the intestine was measured not in inches but in fingerwidths. In fact, in German the name of the duodenum is Zwölffingerdarm and in Dutch the name is twaalfvingerige darm, both meaning "twelve-finger bowel".
The importance of 12 in Judaism and Christianity can be found in the Bible. The biblical Jacob had 12 sons, who were the progenitors of the Twelve Tribes of Israel, while the New Testament describes twelve apostles of Jesus; when Judas Iscariot was disgraced, a meeting was held (Acts) to add Matthias to complete the number twelve once more. (Today, The Church of Jesus Christ of Latter-day Saints has a Quorum of the Twelve Apostles.). In Orthodox Judaism, 12 also signifies the age a girl matures (bat mitzvah)
In Twelver Shi'a Islam, there are twelve Imams, legitimate successors of the prophet Muhammad. These twelve early leaders of Islam are—Ali, Hasan, Husayn, and nine of Husayn's descendants. The Chinese use a 12 year cycle for time-reckoning called Earthly Branches.
The band 'The Number 12 Looks Like You' tried to start 'Mathcore' and as you might have guesed - failed!