The structure of a carbon molecule is a hexagon.

Six:
origin Old English siex, six, syx, of Germanic origin; related to Dutch zes and German sechs, from an Indo-European root shared by Latin sex and Greek hex.

Hexagon:
– origin late 16th cent.: via late Latin from Greek hexagōnon, neuter (used as a noun) of hexagōnos ‘six-angled.’