en_tn_condensed/jer/20/09.md

I will not speak any longer in his name

Possible meanings are 1) "I will never mention Yahweh or say anything about him" or 2) the word "name" represents authority. Alternate translation: "I will no longer speak as his messenger" (See: rc://en/ta/man/jit/figs-metonymy)

it is like a burning fire in my heart, held within my bones

Here the words "heart" and "bones" represent Jeremiah's innermost being. Jeremiah speaks of being unable to not speak Yahweh's message as if Yahweh's message were a fire that burns within him. Alternate translation: "Yahweh's word is like a fire that burns deep within me" (See: rc://en/ta/man/jit/figs-synecdoche and rc://en/ta/man/jit/figs-metaphor)