*I went into some reputable medical sites to find out if there is anything to "pumping" other than novelty and, surprisingly, the answer is yes. There are medical grade vacuum pumps which cost a fortune and can, with a prescribed ongoing routine, make a significant degree of permanent change. What they do, as far as I can tell, is exercise the penis much like weight training to maximize one's DNA limited potential, opening (or re-opening) the "corpora cavernosa" that are the basis of a "boner".
*I looked further and found devices under the name "Bathmate" that are negative pressure hydraulic (water) pumps, which are far stronger than air vacuum pumps. here's a SFW video about it.
The actual product looks like this.

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