The thing about the three somatotypes is that they are as broad as can be. And while that does mean that there is no easy alias for them, it does make them a good set of umbrella tags for the tag group:figures. So implakashens (had no idea how to spell this, so I did it phonetically) is a good idea.

So I decided to list every official rekennised (I did it again) figure tag with each somatotype. But before I do, I will say that I will also be doing the double types, sense that gives us more to work with. And I will be doing those after the mono types. I will not be doing the middle of all three though, because that would just be "average", which this site does not consider tag worthy.

Mesomorph

• Muscular
• Big_muscles
• Huge_muscles
• Hyper_muscles

Ectomorph

• Emaciated
• Skinny
• Slim

Endomorph

• Slightly_chubby
• Overweight
• Obese
• Morbidly_obese
• Curvy_figure (shouldn't actually be included, but most of it's sup tags should, with the exception of one, to be shown later.)
• Hourglass_figure
• Venus_figure
• Voluptuous_figure
• Short_stack

For the naming of the double types, sense the standard arrangement of the types puts mesomorphs on top of the triangle, endomorphs on the bottom-left, and ectomorphs on the bottom-right, I will name them in clockwise fashion. So: meso-ectomorph, ecto-endomorph and endo-mesomorph. There inverses (ecto-mesomoeph, endo-ectomorph, meso-endomorph) would be aliased to them, of course.

Meso-ectomorph

• Athletic

Ecto-endomorph

• Pear-shaped_figure
• Teapot_(body_type)
• Bottom_heavy (if lower half is fatty)
• Top_heavy (if breast based)

Endo-mesomorph

• Musclegut
• Stocky
• Bottom_heavy (if lower half is muscler)
• Top_heavy (if muscle based)

Top_heavy honestly covers two very different tap of bodies, and should probably be two tags.

I don't know how much you want to count the breasts for the somatotypes, but I did for the sake of example.

I honestly believe there could be more tags that are not yet rekenised (English spelling is stupid, and atuo-create does not take sounds into account), so please suggest any tag to fit in.

I am also assuming that there are good reasons why some of these tags do not imply each other.

My understanding was that, despite how it gets frequently used, ecto/meso/endomorph didn't have to do with weight as much as shape, proportions, and fat distribution. An analogy with dogs- greyhounds and labradors are built very different, but they both can still be overweight or emaciated.

That aside, I don't think these would be terribly useful tags. Ecto/endomorph are too similar in sound and their roots aren't super intuitive (outside-shape vs inside-shape?) meaning they'll get misused constantly. And then the combo ones on top? It'd be a huge mess.
Also I don't think that they're super useful categories anyway. They don't reflect real life, and when you add stylization on top it's just kinda irrelevant.