记不起又忘不掉
[jì bù qĭ yòu wàng bù diào]
A rather melancholic tone is conveyed by this nickname. It suggests there are things that linger in one's memory, though they're too obscure or vague to be recalled clearly, but still persist enough to not be completely forgotten. It may describe an ambiguous feeling or experience that is unforgettable even if the exact details escape remembrance.