From megas (great) and aucheo (to boast). To make great boasts, to brag extravagantly. James uses this word of the tongue's destructive potential.
James declares that the tongue is a small member but 'boasts of great things' (James 3:5). Despite its small size, the tongue can set the course of a person's life on fire. This word warns against the disproportionate power of speech — small words can cause enormous damage. The remedy is wisdom from above: pure, peaceable, gentle, and full of mercy (James 3:17).