What is the X in X-mas?
Old English cin, cinn "chin" (but in some compounds suggesting an older, broader sense of "jawbone"); a general Germanic word (cf. Old Saxon and Old High German kinni; Old Norse kinn; German Kinn "chin;" Gothic kinnus "cheek"), from PIE root *genu- "chin, jawbone" (cf. Sanskrit hanuh, Avestan zanu- "chin;" Armenian cnawt "jawbone, cheek;" Lithuanian žándas "jawbone;" Greek genus "lower jaw," geneion "chin;" Old Irish gin "mouth," Welsh gen "jawbone, chin").
1590s, "to press (affectionately) chin to chin," from chin (n.). Meaning "to bring to the chin" (of a fiddle) is from 1869. Slang meaning "talk, gossip" is from 1883, American English. Related: Chinned; chinning. Athletic sense of "raise one's chin over" (a raised bar, for exercise) is from 1880s.
The prominence formed by the anterior projection of the lower jaw.
fretless Chinese board zither with seven strings. Traditionally the body of the qin was of a length that represented the 365 days of the year (3 chi [a chi is a Chinese foot], 6 cun [a cun is a Chinese inch, one-tenth of a chi], and 5 fen [a fen is one-tenth of a Chinese inch] long). The qin is usually lacquered and is inlaid with 13 dots (hui) of ivory, jade, or mother-of-pearl that indicate pitch positions, primarily on the upper melodic string. The silk strings, which are of graduated thickness, are tuned pentatonically, and the thickest string is farthest from the player's body. They are stretched over a narrow and slightly convex sound board, usually made of paulownia wood (Sterculia plantanifolia); the underside of the sound board is closed by a flat base, usually made of zi (Chinese catalpa, Catalpa kaempferi). The underside of the base has two sound holes, the larger of which is called the "dragon pond" (longchi), and the smaller of which is called the "phoenix pool" (fengzhao). The qin's high bridge near the wide end of the soundboard is called the "great mountain" (yueshan), the low bridge at the narrow end is called the "dragon's gums" (longyin), and the two pegs for fastening the strings are called the "goose feet" (yanzhu). Each qin is given a unique name, which is engraved on the back side of the instrument, along with poems and the owner's (or owners') seals