Nugget

google

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mid 19th century: apparently from dialect nug ‘lump’, of unknown origin.

wiktionary

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Probably a diminutive of dialectal nug(“lump, block”) +‎ -et.

etymonline

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nugget (n.)

1852, "lump of gold," probably from southwestern England dialectal nug "lump," a word of unknown origin [OED]. Another theory is that it is from a misdivision of an ingot. Transferred sense (of truth, etc.) is from 1859.