「Crescent, bowed shape, arc」with「long straight line」「black」or「a great distance.」「Arc with long straight line」refers to a GEOMETRIC CHORD SHAPE, defined as a line segment joining two points on any curve, such as a BOWSTRING, the first or last quarter phases of the Moon (add「black」and「a great distance」).
　HYPOTENUSE, the longest side of a right triangle, the side opposite the right angle, is derived from the shape of these elements taken literally, that of the bandages binding the「black」and gangrenous, no-longer-integrated feet of a service provider with「long, sticky fibers」:
　「To enable the size of the feet to be reduced, the toes on each foot were curled under, then pressed with great force downwards and squeezed into the sole of the foot until the toes broke. The broken toes were held tightly against the sole of the foot while the foot was then drawn down straight with the leg and the arch forcibly broken. The bandages were repeatedly wound in a figure-eight movement, starting at the inside of the foot at the instep, then carried over the toes, under the foot, and around the heel, the freshly broken toes being pressed tightly into the sole of the foot. At each pass around the foot, the binding cloth was tightened, pulling the ball of the foot and the heel together, causing the broken foot to fold at the arch, and pressing the toes underneath.」
　　[　https://en.wikipedia.org/wiki/Foot_binding 2012-12-17　]　
　The use of CHORD as a musical term derives from this geometric shape formed by stringed instruments.「Striking a chord」referred to whacking a concubine's foot to make a point understood, not making music, although she may have hollered out a note or two as a 'singing girl.'
　A DIVA is a highly distinguished female singer, and the word originates from「divine, a goddess, a really good singing girl」who was trained as the apprentice of a divining female, the local shaman witch doctor…「singing girl」is a euphemism for a superb sexual services provider, perhaps since she can use her tongue so well or because she causes her clientele to cry out loud and burst into hollering song. Shamans sold the services of these girls, and sold the girls themselves, too…called 'witch doctors' because they also sold divination services along with sex, and attempted to doctor you up after you contracted a sexually transmitted infectious disease.

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: bow string; string of musical instrument; watch spring; chord (segment of curve); hypotenuse
Japanese: bowstring, stringed instrument, chord, hypotenuse, bail, diagonal levelling wire across the top of a masu
Unihan extended: string; hypotenuse, crescent
EDRDG: bowstring; chord; hypotenuse