... 午とは、干支（十二支）の7番目。年・日・時刻などにあてる。方角の名で「南」。陰暦5月の異称。ご。

午年とは、西暦年を12で割った際、余りが10となる年。

「杵（きね）」の原字で、上下に交差し、もちをつく杵を描いたもの。
十二進法では、前半（午前）が終わり後半（午後）が始まる位置にあり、その交差点を「正午」という。
つまり、十二支の中間に位置し、草木の成長期が終わり、衰えを見せ始めた状態を表したものと考えられる。

これを「馬」としたのは、無学の庶民に十二支を浸透させるため、動物の名前を当てたものであるが、順番や選ばれた理由は定かではない。

'Uma' (午) is the seventh of the Chinese zodiacs. It also refers to years, days, times and the like. As a directional name, it stands for "south". In the lunar calendar, it is a designation for the fifth month.

In dividing the Gregorian calendar by 12 (i.e. the number of Chinese zodiac years), the horse year occurs every 10 years.

The origins of the character for 'hammer' (杵) illustrates the stopping intersection point between up-and-down motions in pounding rice; in the duodecimal system, 'shougo' (正午) refers to the intersecting point where the first half of the number has ended and the second half begins.

In short, 'shougo' is thought as constituting the time in the midst of the 12th Chinese zodiac, when vegetations cease to grow and begin to die off.

Due to the widespread illiteracy of the common folk, the name for the animal ('uma') 'horse' (馬) came to be referred to as the 'uma' (午) of the Chinese zodiacs. However the order is uncertain, i.e. whether 馬 or 午 was used first.