What does "stagnation in the prostate" as described as a clinical symptom in serious evidence-based medicine mean? Or is this just a "pop-culture and mass-media" buzzword?
You can search using operators "site:gov" or "site:edu" and find texts, such as this one from PubMed:
Sexual behaviors represent potential modifiable risk factors and may influence prostate cancer development through a variety of specific mechanisms. One biological mechanism involves prostatic accumulation of potentially carcinogenic secretions, which may create more opportunity for prostate cancer development, sometimes referred to as the prostate stagnation hypothesis.
The term "blood stagnation" is not related to prostate stagnation hypothesis and is mentioned as a problem after prostate cancer surgery, for example in this article about acupuncture treatment after prostate surgery.