Perhaps「curtain」of「two」「bite」and「sitting person (匕 so popular in dynastic China)」as the LABIA, the LIPS, both on a mouth for biting and where a concubine sits. FURROWS or a FURROWED SHAPE as a spot that is plowed by a pointed tool…. All sets of lips as the STARTING POINT for intercourse activities (verbal or sexual) leading to CONCEPTION (of ideas or gametes). Traditionally in Asian cultures, one's age was reckoned from the time of CONCEPTION and joining of the sperm and ovum, not with parturition or birth, clearly the STARTING POINT.
Also the ancient Chinese zodiac sign of the DRAGON, likely depicting the dragon's lair, and where he may be found most of the time. Asian dragons have no wings, resembling large snake-like spermatozoon that「bite」onto an ovum in the attempt at fertilization…the ancient Chinese「more than 3,500 years before the 'father of modern microscopy' was born…achieved magnification levels of 150 times today's standard…」
[ https://www.microscope.com/about-microscopes-t-19.html 2011-04-23 ] The Chinese knew about ovum fertilization, and the DRAGON was that spirit of life.
「Person sitting with mattock to cut furrowed slits into the side of a cliff」as a terraced slope holding wetland paddies as the start and CONCEPTION of FARMING, the STARTING POINT of civilization (that literally means「living politely with folks whom you do not know」) and the end of hunter-gatherer society—human beings began to settle. By cutting FURROWS into the soil forming terraced slopes, farming areas in horizontal lines, creating flat spaces, later dammed with small dikes that traversed the entire slope horizontally and from top to bottom, where water collected naturally as the rains fell and then「branched downwards」to follow a system of small irrigation channels.
DRAGON has another meaning in the Chinese astrological zodiac since antiquity due to an association with chi (气) that are flows of earthly power moving up and down large hills, with the path of the DRAGON following the path taken naturally by flowing water that is「branching down」the slope, as depicted by this glyph.
「Furrowed, slit with lips」refers unmistakably to the female human vaginal opening into which the snake-like dragon enters, once more as THE STARTING POINT, the MEANS TO START, CONCEIVE.
Minor meaning of CLAM, perhaps as a「juicy slit with lips」and what it resembles.
(1) 子 rat (children, spermatozoa)
(2) 丑 cattle (herded meat assets, harem)
(3) 寅 tiger (religious dogma, enslavement)
(4) 卯 rabbit (female, reproduction)
(5) 辰 dragon (power sex)
(6) 巳 snake (fornication)
(7) 午 horse (autoeroticism)
(8) 未 sheep (zooerastia)
(9) 申 monkey (deities, anal-centric)
(10) 酉 cock (cognitive processing impairment)
(11) 戌 dog (male, domination)
(12) 亥 swine (humanity in general).

External source definitions …excluding politically incorrect concepts and other meanings deemed offensive today; may include extended definitions, euphemisms, and mnemonics)
Chinese: 5th earthly branch: 7-9 a.m., 3rd solar month (5th April-4th May), year of the Dragon
Japanese EDRDG: sign of the dragon, 7-9AM, fifth sign of Chinese zodiac
Unihan extended: early morning; 5th terrestrial branch

Used within names (nanori)
とき　･　のぶ　･　のぶる