an adamant (mythical rock thought to be of impenetrable hardness) · something extremely solid and indestructible · the firmness of one's own spirit and the strength of one's own spiritual power
köken: /komʉ kau/ → /koŋɡau/ → /koŋɡɔː/ → /koŋɡoː/ From Middle Chinese 金剛 (MC kim kang), itself a translation of Sanskrit वज्र (vajra, “diamond, adamant; thunderbolt”). Compare modern Cantonese 金剛 /金刚 (gam¹ gong¹).
Borrowed from Old East Slavic адамантъ (adamantŭ), ultimately from Ancient Greek ἀδάμας (adámas). See the more modern form deimantas, from the same source through French.