Ligaments at the posterior superior iliac spine
It seems from the description in Kumar, et al. (2014) that the "dimples of venus ligament(s)" are connected to the skin, and seeing that ligaments are fibrous connective tissues that normally connect bones to other bones, I am intrigued to know more. What is the name of these "dimple of venus ligaments" and what is their purpose?


First, re: what a ligament is, you're correct in your understanding that ligaments generally bind bones to bones (vs. tendons), but the term is used more broadly as connective tissue that binds things together, holds them in place, is a remnant of a fetal structure, or a mesenteric fold. Your wikipedia link acknowledges this. Some examples are:


Round ligament of the liver: a remnant of fetal structure
Broad ligament of the uterus: a mesenteric fold
Median arcuate ligament: this one actually binds two muscles together
Sternopericardial ligament: binds the pericardium to the sternum


The unnamed short ligaments Kumar describes (and wikipedia, quora, and stack exchange have repeated), are probably unnamed because they are difficult to isolate and study, and they are not clinically relevant. They may even be theoretical. There are no studies on them indexed in medline, and they aren't discussed in any anatomy text I've read. Dimples are generally thought to be caused by fibrous connections between the skin and muscle, bone, or other deep tissue. If you ever cut into the back of a cadaver or surgical patient, you'll see that there are a great number of unnamed fibrous connections to the skin. It's not unreasonable for Kumar to invoke them as the cause for these dimples.