Read the background to this post over at my Persian blog. To sum up, “Dzhokhar” is a transliteration of an Arabic word, جَوهَر (jawhar), that was loaned from Arabic to Persian after first being loaned from Persian to Arabic. The original Persian word is gawhar, meaning “jewel” or “essence.” At some point (I think pre-Islam, because unless I’m wrong the word appears in pre-Islamic Arab poetry, although those were only compiled in written form post-Islam so who knows?) Arabs must have picked up this word from the Persians, but changed the first consonant to a “j” sound since there’s no hard “g” sound in Arabic (the Egyptian dialect pronounces the letter jeem, which in standard Arabic and most dialects has a “j” sound, like a hard “g,” and in Gulf dialect the “qaf” can sound like a compromise between “q” and “g,” but there’s no hard “g” in the formal tongue). This is interesting, because Arabic generally changes foreign hard “g” sounds into the “gh” consonant (Pythagoras = فيثاغورَس (fīthāghūras; there’s no “p” sound either, so that becomes an “f” sound!), but for whatever reason in this case it became a “j” sound. Later, presumably after the Arab armies had conquered Iran and destroyed the Persian Empire, جَوهَر was incorporated into Persian as a new loanword, but with the emphasis on the meaning of “essence” since they were still using gawhar to mean “jewel.”

جَوهَر means “essence,” “nature,” “content,” “substance,” “matter,” or “jewel.” It also forms a rare quadriliteral (four-letter) Arabic root; these usually come about through loanwords, and in this case جَوهَرَ (jawhara) means “to become substance.” The abstract form جَوهَري (jawharī) means “substantial,” “essential,” or the more concrete “jeweler,” which can also be translated as جَوهَرجي (jawharjī), or jawhar plus the Turkish ending “-ji,” which is akin to the “-er” ending in English and here signifies occupation. Speaking of Turkish, the passive participle of جَوهَرَ, which is مُجَوهَر (mujawhar), means “bejeweled” in Arabic but was borrowed by Turkish to mean “jewel.”

UPDATE: More here, and here.