Old English sioloc, seoloc "silk," ultimately from an Asian word (cf. Chinese si "silk," Manchurian sirghe, Mongolian sirkek) borrowed into Greek as serikos "silken," serikon "silk" (cf. Greek Seres, a name for an oriental people from whom the Greeks got silk). Also found in Old Norse silki but not elsewhere in Germanic.
According to some sources, the use of -l- instead of -r- in the Balto-Slavic form of the word (cf. Old Church Slavonic šelku, Lithuanian šilkai) passed into English via the Baltic trade and may reflect a Chinese dialectal form, or a Slavic alteration of the Greek word. But the Slavic linguist Vasmer dismisses that, based on the initial sh- in the Slavic words, and suggests the Slavic words are from Scandinavian rather than the reverse.
Western cultivation began 552 C.E., when agents from Byzantium impersonating monks smuggled silkworms and mulberry leaves out of China. In reference to the "hair" of corn, 1660s, American English. Figurative use of silk-stocking (adj.) for "wealthy" is attested from 1798, American English. Silk-screen is first attested 1930. Silk road so called in English from 1931.