An archaic or dialectal word meaning to know or learn; or in modern usage, internet slang for a small truth or fact.
From Old English 'witan' (to know). This is an extremely old word, cognate with German 'wissen' and related to Latin 'videre' (to see). Modern internet usage is a playful revival of this ancient word.
The word 'weet' connects back to the same root as 'wit' (as in 'to wit,' meaning 'namely'), which goes back thousands of years. Internet users reviving it is a funny example of how slang circles back to historical language.
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