'semicircular' originates from Latin, specifically the word 'semicirculus,' where 'semi-' meant 'half' and 'circulus' meant 'circle.'

'semicirculus' transformed into the Old French word 'semicirculer,' and eventually became the modern English word 'semicircular' through Middle English.

Initially, it meant 'half of a circle,' and this meaning has largely remained the same in modern usage.