「Down on all fours」in a「rolling stream」of motion describes a long series of kowtows that everyone was required to perform PRIOR TO, IN ADVANCE of an audience with the Chinese emperor (the 'lord' portion of the word 'lordosis') meaning TO GIVE TO ANOTHER something intangible, such as giving another respect by kneeling on all fours with the head down. One source described the method in China as kneeling or lying prostrate and while down on the floor, touching your forehead to the floor three times, returning to a standing position, then kneeling and kowtowing again, etc., also performed three times (the「three kneelings and nine kowtows」)…there may be many other kowtow explanations, but the exact method used is not too important any longer, since no emperor currently rules. Note that there are other glyphs that represent kowtowing.
Meaning TO GIVE TO ANOTHER something intangible, or oneself, such as giving an OPPORTUNITY by bowing on all fours with the head down. TO MANIFEST as in CLEARLY APPARENT to everyone's sight or understanding of an intention, making OBVIOUS what is desired, to SHOW OR DEMONSTRATE PLAINLY. Human beings with arms and legs「get down on elbows and knees」and present the lordosis position, an action that occurs PRIOR TO, IN ADVANCE of「rolling streams」of copulation on all fours during mating of many animal species such as the primates (baboons, bonobos, human beings, gorillas), felines (cats), equines (horses), canines (dogs), rodents, rhinoceros, and so on. LORDOSIS is the characteristic position that a female animal in estrus adopts to MANIFEST, MAKE CLEARLY APPARENT AND OBVIOUS a willingness to mate by lifting her tail while arching or stiffening her back, exposing the perineum whilst physically spreading both her anus and vulva, allowing her to assume a stable position BEFORE, IN ADVANCE OF, PRIOR TO being mounted from behind by a male with an erection and/or a readied baculum in the case of animals so naturally equipped. Of course, with human animals, this position is also at times associated additionally with males, transgenders, or other they(s), WE(s), I(s) and ME(s) desirous of attracting a copulation partner with which to engage in some manner: see for yourself if you do not believe so, sometime on a busy sidewalk or in a park setting, just to see what sort of animals are attracted (as well as the police).
Note the relationship of this glyph, with「stream」(亅) drawn connected with and inside「rolling, rolled back」(乛) element to mean PRIOR (as it is with「male」丁) compared with these exact same elements drawn as if the stream has been discharged in the glyph meaning 'completed action, come to the end, finished, the end, achieved the goal, ejaculation, a clear understanding' (了).
Moreover, the use of this glyph as an element in glyphs meaning to spear, to be speared (矛), meaty displays on a carnival float during a festival (矛), squeezing juices to relieve (抒), a handsome woman (妤), a back-and-forth shuttling motion (杼), and so on with every other use as an element indicate lordosis. The Chinese engaged in sexual intercourse with the submissive person naturally in the lordosis position (「primate-style, doggy-style」), and not the missionary position demanded for some odd reason thousands of years later by the Christian missionaries.

External source definitions …excluding politically incorrect concepts and other meanings deemed offensive today; may include extended definitions, euphemisms, and mnemonics)
Chinese: to give; (archaic) I; me
Japanese EDRDG: beforehand, previous, myself, I
Unihan extended: I, me; to give