「Multiple crotches」and「fitting, suitable, proper, correct」…a clear description of anything that is PILED in meaty stacked layers under the control of a shaman on matting and mattresses. An ACTION OR ACTIVITY THAT IS REPEATED TIME AND TIME AGAIN such as might be expected to occur with「many crotches surrounding as a temporary meat pile」and「in control of a pile of obedient crotches」as the lord of the harem.
　Interestingly, the Chinese glyph (疊) with meaning similar to this glyph does not refer to tatami or matting at all—the word 'tatami' and its meaning were added by the Japanese many centuries later. This glyph must have meant something else formerly, such as「plugging orifices surrounded by abdomen, meat pile」and after use, FOLDED INTO LAYERS for storage (TO SHUT, PUT AWAY) and REPEATING, DUPLICATING use of the same mat (and so on) again and again.
　Moreover, the outside surfaces of tatami mats are not woven from rice straw at all (too brittle, too short) but rather, from split igusa reeds…rice straw may have been bundled and simply packed within the woven reeds, but more likely the filler was some sort of batting or hemp cloth since dry straw would quickly flatten and crumble after only a few uses, losing its effectiveness for repeated use (today, the filler-batting is usually replaced by synthetic materials). Moreover, tatami mats cannot be folded, but some other type of softer mat could be FOLDED IN LAYERS.
　Nevertheless, top element is「many crotches」tripled as in very many of them. Note that in Japanese vernacular, the word for「wetlands」manko 漫湖, refers to a vagina as 'the other orifice' for filling and plugging within a wet area.
　Glyph in Japan depicts the mat itself, and not the plant material from which the mats were made, as perhaps another oblique reference to the USE OF MATS upon cavern floors, where sat the shaman's service providers each with her wetland atop a mat,「crotches, surrounding piles of meat」or「crotches in proper form」by using a mat beneath.
　Older glyphs all with the same meaning include「many crotches accumulated in meat pile」and「alternating between many plugged orifices」(疉) that leave little if any doubt as to what the glyph was referring. Also meaning REPEATED USE, REPEATED ACTION, BENT OVER and ACCUMULATED, clearly a description of a bunch of folks in a FOLDED, BENT-OVER, LAYERED position revealing groins for repeated and easy access by a gang of buddies invited over for the festivities and beers, but likely situated on MATS rather than the rocky cavern floor as perhaps the only connection to what later became tatami-like mats.
　USING MATS necessary for sexual activity would certainly make everything more pleasant for all involved and reduce the number of skinned knees and elbows. The matting could be easily FOLDED or FURLED and put away when not in use, but tatami mats are unbendable and are not removable when not in use.
　Nevertheless, some still claim that the top element as「rice paddy」is an oblique reference to growing rice plants, and growing rice plants as an oblique reference to harvested rice as an oblique reference to the residual straw by-product, a material that was purportedly used for stuffing mats, folding woven single layers of rice straw into thicker layers, and finally surrounding the thickly folded, piled up layers into a mat, none of which is the actual production method of tatami matting.

Modern definitions (that generally disregard history) …excluding politically incorrect concepts and other meanings deemed offensive today; may list only pigeonholed definitions, euphemisms, or meaningless mnemonics)
Chinese: variant of 疊|叠; variant of 疊|叠; to fold; to fold over in layers; to furl; to layer; to pile up; to repeat; to duplicate
Unihan extended: pile; be piled up; fold up
EDRDG: pile; be piled up; fold up