expression
Used as a noun phrase to emphasize the thing or matter itself, often in contrast to related aspects or circumstances.
問題は、そのこと自体よりも、どう対応するかだ。
The issue is not so much the thing itself, but how we deal with it.
彼の言ったこと自体は間違っていない。
What he said itself is not wrong.
自体 is a suffix meaning 'itself' or 'in itself', while こと自体 is a specific phrase meaning 'the thing itself'.
Combination of こと (thing, matter) and 自体 (itself).