'customarily-spread' originates from the combination of 'customarily,' which comes from 'custom,' and 'spread,' which means to extend over a large area.

'customarily' evolved from the Old French word 'costume,' and 'spread' from the Old English 'sprǣdan.'

Initially, 'customarily' meant 'according to custom,' and 'spread' meant 'to extend.' Together, they convey the idea of something being widely accepted or practiced.