'opposite' of 'déjà vu'

Solution 1:

In French, we say 'jamais vue', and Wikipedia shows that the term jamais vu has also been adopted into English, mirroring déjà vu.

We use jamais vu to describe the fact that something has already happened to someone, but he feels like it's the first time.

I often experience the feeling myself when I'm concentrating on a particular word; if I keep repeating it, it begins to feel weird, as if it's not really the right word to use.

Solution 2:

A person may be described / describe themselves as feeling detached from reality, when they realise that the familiar suddenly feels weirdly alien.

SymptomChecker lists quite a few mental disorders which may have this sensation as a symptom, but I'm sure most people have the occasional manifestation, and getting on with everyday life soon corrects one's 'normality settings'.

Solution 3:

The jamais vu experience is similar to alienation.

The Latin word for alien is alienus, "belonging to another." That idea of not belonging, or not fitting in, gave rise to the Latin verb alienare, "to estrange," which alienation comes from.

(vocabulary.com)