Tongue
The tongue's primary functions are enabling us to speak, consume, and taste.
Speech
The tongue's association with our ability to express ourselves is evident from the fact that Latin lingua, Greek glossa, as well as "tongue", all mean both tongue and language.
The power of speech is immense, and the tongue, as potentially harmful in this capacity, is frequently mentioned in the Bible (especially in James 3:5-6). In many religious contexts, not only in the Bible, malicious tongues are considered among the gravest sins.
We have numerous expressions that describe the tongue as a symbol of speech, such as "hold your tongue," "to have something on the tip of your tongue," "tongue in cheek," and "silver-tongued."
Fire
Fireand the tongue are closely associated. God's "tongue is like a consuming fire" (Isaiah 30:27); the Holy Spirit appears as tongues of fire in Acts 2:2-4, enabling the apostles to "speak in tongues," to name a couple of examples from the Bible alone. (There is a strong connection between creativity, tongues, and fire.) At the same time, "tongues of fire" is a synonym for flames, so the association works both ways.