'fernish' originates from the English word 'fern,' specifically the word 'fearn' in Old English, where 'fearn' meant 'fern.'

'fearn' transformed into the Middle English word 'ferne,' and eventually became the modern English word 'fern,' leading to the adjective 'fernish.'

Initially, it meant 'pertaining to ferns,' and this meaning has largely remained the same in modern usage.