The Spanish verb 'olvidar' (to forget) comes from Vulgar Latin '*oblitare', which developed from the Latin participle 'oblitus' (forgotten). This in turn came from the Latin verb 'oblivisci' (to forget), which was formed by combining two elements: the prefix 'ob-' meaning 'against' or 'in front', and 'livisci' meaning 'to become dark or dense'. The metaphorical meaning behind this construction suggests that forgetting something is like it becoming dark or obscured from view - a rather poetic way of describing how memories fade!

The word 'olvido' (noun meaning 'forgetfulness' or 'oblivion') is directly related to 'olvidar'. You might also encounter 'olvidadizo' (forgetful) and 'inolvidable' (unforgettable), which are all part of the same word family.

The English word 'oblivion' and its related forms like 'oblivious' share the same Latin ancestor as 'olvidar'. While the Spanish word retained its verbal meaning of 'to forget', the English words developed more toward the notion of a state of being forgotten or unaware. You can see how the Latin 'oblivisci' influenced both languages, with English keeping the 'b' sound while Spanish transformed it to a 'v' sound.