I thought she was acting foolishly, but I 'bit my tongue' [='held my tongue'] and didn't say anything.
The news of their engagement 'set tongues wagging'. = 'Tongues were wagging' over their engagement.
He speaks English fluently but his 'mother tongue' [='native language, first language'] is Chinese.
(..) and bid me hold my peace I pray you both, if you have hitherto concealed this sight, let it be held within your silence still And whatsoever else shall pass tonight, give it an understanding but no tongue Upon the platform 'twixt eleven and twelve I'll visit you - Our duty to your honour (..)2015 Hamlet
(..) than Ito Hercules... within a month! Oh most wicked speed, to post with such dexterity to incestuous sheets It is not, nor cannot come to good. But break, my heart, for I must hold my tongue - Soft you, a word, my lord - Horatio? Friends to this ground and liegemen to the Dane (..)2015 Hamlet