'commonly-thought' originates from the combination of 'common' and 'thought', where 'common' meant 'shared by all' and 'thought' referred to 'the act of thinking'.

'commonly-thought' evolved from the Old English word 'geþoht', which meant 'thought', and 'common', which has remained largely unchanged.

Initially, it meant 'a thought shared by many', but over time it evolved into its current meaning of 'widely believed or accepted'.