'bicolour' originates from English formation combining the prefix 'bi-' (from Latin 'bis' meaning 'two' or 'twice') and 'colour' (from Old French 'colour', ultimately from Latin 'color' meaning 'colour').

'colour' came into English via Old French 'colour' from Latin 'color'; the prefix 'bi-' comes from Latin 'bis'. These elements were combined in English to form 'bicolour' (parallel to 'bicolor' in US spelling).

Initially formed to mean 'having two colours', the meaning has remained essentially the same: 'consisting of or exhibiting two colours'.