ingrainyoudaoicibaDictYouDict[ingrain 词源字典]
ingrain: [17] Ingrain means literally ‘work into the grain’ (of fabric, originally) – whence the main metaphorical sense of ingrained, ‘deepseated’. But there is much more to the story of ingrain than that. Its ultimate source was engrainer ‘dye’, an Old French verb based on graine ‘cochineal dye’. English borrowed this in the 14th century as engrain ‘dye crimson with cochineal’, which remained a live sense of the word into the 17th century.

Gradually awareness of the word’s original specific connections with the colour crimson died out, and the verb was virtually formed anew in the mid 17th century using the concept of the grain or ‘texture’ of cloth, but the spelling engrain remained, and remains as a secondary variant to this day, to remind us of the word’s origins.
=> grain[ingrain etymology, ingrain origin, 英语词源]
ingrain (v.)youdaoicibaDictYouDict
1766, see engrain. Figurative use, of qualities, habits, etc., attested from 1851 (in ingrained). Of dyed carpets, etc., 1766, from in grain.