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.
(..) see you, And... and I think you're beautiful, and I, um... I feel really warm when I am around you, And, um, my tongue swells up. So... Do you wanna go eat food? Do I... do I wanna eat food? Mm-hmm. You know, uh, the code... food. (..)2003 Elf