'unusual' originates from Latin, specifically the word 'usualis,' where 'un-' meant 'not' and 'usualis' meant 'customary.' 'Related' comes from Latin 'relatus,' the past participle of 'referre,' meaning 'to bring back.'

'Unusual' changed from the Old French word 'usuel' and eventually became the modern English word 'unusual.' 'Related' evolved from the Latin 'relatus' through Old French 'relater.'

Initially, 'unusual' meant 'not according to custom,' and this meaning has largely remained the same in modern usage. 'Related' initially meant 'brought back' and evolved to mean 'connected or associated.'