Plural of tongue: the flexible muscle in your mouth used for tasting and speaking; languages; or pointed projections resembling a tongue.
From Old English 'tunge,' related to Germanic and Indo-European roots meaning the same thing. The word has been used metaphorically for languages since ancient times because the tongue is the organ of speech.
We call languages 'tongues' (like 'speaking in tongues') because your actual tongue is what makes the sounds—so metaphorically, your language is your tongue, which is why we talk about 'mother tongue' as your first language.
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