chemicalyoudaoicibaDictYouDict[chemical 词源字典]
chemical: [16] Essentially chemical, and the related chemistry and chemist, come from alchemy with the initial al- dropped. Alchemy itself is of Arabic origin; al represents the Arabic definite article ‘the’, while the second element was borrowed from Greek khēmíā ‘alchemy’. Loss of al- seems to have taken place originally in French, so the immediate source of the English words was French chimiste and chimique (whence the now obsolete English chemic, on which chemical was based).

At first this whole group of words continued to be used in the same sense as its progenitor alchemy; it is not really until the 17th century that we find it being consistently applied to what we would now recognize as the scientific discipline of chemistry.
=> alchemy[chemical etymology, chemical origin, 英语词源]
chemical (adj.)youdaoicibaDictYouDict
1570s, "relating to chemistry," from chemic "of alchemy" (a worn-down derivative of Medieval Latin alchimicus; see alchemy) + -al (1). In early use also of alchemy. Related: Chemically.
chemical (n.)youdaoicibaDictYouDict
1747, from chemical (adj.). Related: Chemicals.