Ga8-7	Ga8-8 (*275)	Ga8-9 (213)
18h (273.9), Zhōngshān (274.0)
'20 (354)	'21	'22
"October 18	"19 (292)	"20

Wikipedia gives no explanation for its name, but it is easy to see the general meaning from its Chinese writing:

中山

The first character, looking like a sail on a mast, represents the idea of 'middle' (as in the 'Middle Kingdom' = China). The second character is a picture of 3 mountain peaks and it means 'mountain'. Therefore ο Herculis could represent the 'mountain in the center'.

It may be argued that it is a coincidence, but 80 (days from January 1 to March 21) + 274 = 354, equal to 12 * 29½ nights. In rongorongo a mountain (mauga) type of glyph probably indicates that darkness has fallen (because the luminary in the sky has gone down, is hidden behind the mountains in the west). At the time of G this 'mountain in the middle' (Zhōngshān) rose heliacally nearly exactly at the 18h line.

The Yellow Dragon (the Emperor) evidently is characterized by this sign of 'Middle':

And the quadrangle which delineates the torso of Hercules is divided by the vertical line of 17h. Around 15 * 72 = ca 1100 years ago Zhōngshān must have risen heliacally at 17h.

Intrigued I followed up the idea, and the basic concept described by the character 'in the middle' seems to be an arrow piercing the middle of a target (the bull's eye), according to Kenneth G. Henshall's A Guide to Remembering Japanese Characters:

When the arrow has hit its target its head is inside (ki roto) and cannot be seen.

I think the explanation of why the emperor has no arrow (cfr at Gemini) lies just around the corner:

As emperor of China he ruled the land. His arrow had already been used when he shot it downwards into the paddy-fields to make them fertile:

The paddy-fields are under water but the foot paths across are dry land. This fact makes us understand why the musicians are sitting in a 'bowl' with another type of sign than the the round 'eyes' in the skirt of Pachamama - these rectangles are paddy-fields:

By the way, with a waxing moon face at left and a waning moon face at right (I am referring to those musicians who pairwise face each other inside the wagon) there should be a full moon between them. I think the creator of the picture is alluding to the full moon by way of the sheng instruments - because Pan (with his flute) was said to play at noon ('... Pan with his pipes, the demon of still sun-drenched noon ...'). Instead of a single mouth organ (for Pan at noon) there is a pair of them at full moon.