barbarian, egg
—
蛋 centers on a primitive or uncivilized person (barbarian) and, by extension, the egg of such creatures or simply an egg. The two meanings are linked through the idea of something raw or undeveloped.
protein
century egg; thousand-year old egg; hundred-year old egg; preserved egg (Chinese delicacy)
lipoprotein
low-density lipoprotein; LDL
low-density lipoprotein; LDL
animal protein
nucleoprotein
vegetable protein
seitan; wheat gluten
phosphoprotein
total protein
Tanka people (of southern China)
anabolic steroid
Protein Engineering Research Institute
opal
egg yolk
total serum protein
hyperlipoproteinemia
hyperproteinemia
hen's egg (esp. in Chinese cuisine)
蛋 combines 疋 (a foot or leg) with 虫 (insect/reptile). The exact historical development is uncertain, but it likely originally referred to a type of barbarian tribe, with the egg meaning arising later as a phonetic loan or semantic extension.
A barbarian's foot (疋) stomps on an insect (虫), crushing it like an egg. This links the barbarian and egg meanings through a violent, primitive act.
For タン, imagine a barbarian tanning an egg-shaped leather hide under the sun: tan -> タン.