Fluttering back and forth, such as might be seen of FLAG FRINGES, those golden-colored, finger-like appendages when blown by a breeze. May also refer to literal fingers fluttering, a「method while beside a supine child.」…or, the「method of a child while lying prostrate」also known as DIDDLING: to move back and forth with short rapid motions, jiggling, to copulate with oneself (the 'selfie'), to practice masturbation upon another.
Concept of the FLAGELLATING motions of the fringes of a flag relate to the appearance of millions of spermatozoa against the side of an ovum striving to be the first (and hence the only) gamete to complete the cycle of fertilization and reproduction, the SWIMMING motion of sperm flagella in semen, the「method of doing something multiplying itself」(note the use of「flag」in the word「flagella」is not a coincidence)
「According to an ancient Chinese text, the Chinese viewed magnified specimens through a lens at the end of a tube, which tube was filled with varying levels of water according to the degree of magnification they wished to achieve. Ingenious, effective and repeatable in the home, today. That this occurred some 4,000 years ago in the Chow-Foo dynasty and more than 3,500 years before the 'father of modern microscopy' was born is quite remarkable. That these Chinese ancients achieved magnification levels of 150 times today's standard, or 100 moou, is breath-taking.」
[ https://www.microscope.com/about-microscopes-t-19.html 2011-04-23 ] …the Chinese knew about sperm and ova fertilization:「repeatedly rolling stream」is an excellent description of a huge infestation, but also describes quite well a single SPERMATOZOON in motion. UNFETTERED refers to having no fetters, or foot bindings in place as restraints.
Without a doubt, the Irish also have knowledge of their own to pass along in these trying times:「Masturbation will not spread coronavirus, especially if you wash your hands (and any sex toys) with soap and water for at least 20 seconds before and after.」Nonetheless and regrettably, unlike in dynastic China, it must be undertaken alone to truly be a preventative countermeasure but still achieve the desired result with some degree of safety.
[ https://www.sexualwellbeing.ie/sexual-health/sex-and-coronavirus/ 2020-03-31 ]
The Dutch, too have the same solution—it seems masturbation has become mainstream in the media the world over due to the coronavirus (it has always been 'the main stream' in reality, albeit covertly for most folks):
「'Don't have sex with your partner if they have been isolated because of (suspected) coronavirus infection,' the RVIM says. 'Sex with yourself or with others at a distance is possible (think of telling erotic stories, masturbating together).'」
[ https://www.theguardian.com/world/2020/may/15/dutch-official-advice-to-single-people-find-a-sex-buddy-for-lockdown-coronavirus 2020-05-16 ]
Needless to point out perhaps, but Chinese shamans from antiquity hit upon the same solution as a pandemic preventative countermeasure, honed for ultimate client satisfaction by utilizing naked females with no-longer-integrated feet as masturbatory sex buddies available for short-term rental with erotic visualization of live prepubescent female genitalia engaging in autoerotic stimulation herself, as a solution to the same problem facing us now, but in pre-Internet days.

External source definitions …excluding politically incorrect concepts and other meanings deemed offensive today; may include extended definitions, euphemisms, and mnemonics)
Chinese: scallops along lower edge of flag
Japanese EDRDG: to swim, to move freely, to rove
Unihan extended: to swim; to move or rove freely