Emerald

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Middle English: from Old French e(s)meraud, ultimately via Latin from Greek ( s)maragdos, via Prakrit from Semitic (compare with Hebrew bāreqeṯ, from bāraq ‘flash, sparkle’).

wiktionary

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From Middle English emeraude, borrowed from Old French esmeraude, from Vulgar Latin *smaralda,  *smaraldus,  *smaraudus, variant of Latin smaragdus, from Ancient Greek σμάραγδος(smáragdos),  μάραγδος(máragdos), from a Semitic language. Compare Hebrew בָּרֶקֶת‎ (bareket, “emerald, flashing gem”), Akkadian 𒁀𒊏𒄣(baraqu, literally “scintillation”), Arabic بَرْق‎ (barq, literally “flashing”), Egyptian bwyrqꜣ(literally “to sparkle”):

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and loanwords with Semitic etymon such as Sanskrit मरकत(marakata) and Persian زمرد‎ (zomorrod) (whence Turkish zümrüt and Russian изумру́д(izumrúd)). 

etymonline

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emerald (n.)

"bright green precious stone," c. 1300, emeraude, from Old French esmeraude (12c.), from Medieval Latin esmaraldus, from Latin smaragdus, from Greek smaragdos "green gem" (emerald or malachite), from Semitic baraq "shine" (compare Hebrew bareqeth "emerald," Arabic barq "lightning").

Sanskrit maragdam "emerald" is from the same source, as is Persian zumurrud, whence Turkish zümrüd, source of Russian izumrud "emerald." For the unetymological e-, see e-.

In early examples the word, like most other names of precious stones, is of vague meaning; the mediæval references to the stone are often based upon the descriptions given by classical writers of the smaragdus, the identity of which with our emerald is doubtful. [OED]

Emerald Isle for "Ireland" is from 1795.