From Latin 'factionem' (a making), from 'facere' (to make) — originally 'a way of making,' then 'manner,' then 'prevailing style.'
A prevailing custom or style of dress, behavior, or way of life; to make or shape something into a particular form.
From Old French 'façon' (shape, manner, style), from Latin 'factio' (a making, a doing, a group that acts together), from 'facere' (to make, to do). The PIE root is *dheh₁- meaning 'to put, to place, to do, to make,' one of the most productive roots in all of Indo-European. From this root come Latin 'facere' (to do), Greek 'tithenai' (to place), Sanskrit 'dadhati' (places
'Fashion' and 'faction' are doublets — both descend from Latin 'factiō' (a making; a group). 'Fashion' came through Old French (where the 'ct' softened to 'ç'), while 'faction' was borrowed later directly from Latin. A 'fashion' is literally a 'way of making,' and a 'faction' is a group that 'makes' or 'does' things together