「Passing through feet」or「orifice in skin fold of no-longer-integrated foot」with「pass through completely, shitcan」that today is used as LEAP, although the original intent from China perhaps was to「lift both feet into the air and allow them to remain there」while the client MANIPULATED them in his hands and masturbated using the artificial vagina formed in the deep skin fold of one foot and then the other as the girl lay prostrate, otherwise known as DANCING WITH THE STARS. Nevertheless, elements suggest that an opportunity「opened up」that no longer required the use of a no-longer-integrated foot and hence the feet were「spread open」as the client LEAPED AT THE CHANCE to access what was made available while the service provider was「down on all fours, the shitcan with rod in meat.」
Japanese adds MANIPULATE (to use hands and handle with some skill), and REPEATING THE SAME ACTION or a REPEAT PERFORMANCE, that also might describe the same motions of feet and hands repeated again and again in a DANCE STEP or particular DANCING STYLE such as the waltz, tango, jitterbug, twist, bump and grind, etc. There is little doubt that one obvious purpose of modern dancing is sexual allure, and really old dancing, too for that matter.
「Orifice with erotica」and「lordosis in use, ass bucket, rod in mooning meat」details booty-shaking, twerking, and mooning to attract or manipulate potential sexual partner(s) for the moment, males and females LEAPING AT AN OPPORTUNITY that presents itself, and REPEATING THE SAME PERFORMANCE with as many as possible until exhaustion, all descriptive of how both the males and females of many species copulate, MATING DANCES in what is more politely referred to as COURTSHIP DISPLAYS.
As depicted in erotic Chinese art, men in dynastic China masturbated by wrapping no-longer-integrated feet around an erect penis:「Bound feet were once considered intensely erotic in Chinese culture. …The process was started before the arch of the foot had a chance to develop fully, usually between the ages of 2 and 5. …Qing Dynasty sex manuals listed 48 different ways of playing with women's [no-longer-integrated] bound feet」(after removing the binding cloths, of course)
[ https://en.wikipedia.org/wiki/Foot_binding 2012-12-17 ]

External source definitions …excluding politically incorrect concepts and other meanings deemed offensive today; may include extended definitions, euphemisms, and mnemonics)
Chinese: leap; leap
Japanese EDRDG: jump, dance, leap, skip
Unihan extended: leap, jump