Conflict is, at its root, a collision. The word comes from Latin confligere — con- meaning 'together' and fligere meaning 'to strike'. Two forces, striking each other simultaneously.
The Latin fligere appears to derive from a Proto-Indo-European root meaning 'to strike' or 'to hit'. It produced a small but violent family of English words: afflict (to strike at someone), inflict (to strike something upon someone), and the less obvious profligate — from Latin profligare 'to strike down', which evolved through 'to ruin' to its modern meaning of 'recklessly wasteful'.
Conflict entered English in the 15th century, initially meaning physical armed combat. The broadening to include verbal disagreement and psychological tension came later, as the physical metaphor proved irresistible. We still speak of 'clashing opinions', 'striking a nerve', and 'coming to blows' over ideas.
The etymology reveals something about how humans understand disagreement: as fundamentally physical. Even our most abstract conflicts — moral, political, philosophical — are described in the language of bodies hitting bodies.