Tweet

google

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mid 19th century: imitative.

wiktionary

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Onomatopoeic of the sound made by a  bird. Compare  twitter. The social media senses evolved from earlier Twitter update,  twit(noun),  twitter(verb). [1]

etymonline

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tweet (n.)

1845, imitative of the sound made by a small bird. As a verb by 1872. Related: Tweeted; tweeting. As the word for what one does on the Twitter microblogging service, by 2007.