• 個人こじん — individual (person)
• 一個いっこ — one piece / item
• 別個べっこ — separately / another one
• 個体こたい — individual body / solid (state)
• 個性こせい — individuality / personality
• 何個なんこ — how many (small items)

The left side 亻 indicates “person,” and the right side 固 gives the sound (コ). Together, 個 refers to something discrete or distinct—hence its use as a counter and for “individual.”

一個いっこだけ 残のこっています。
Only one piece remains.

彼かれは 個性こせいが 強つよい。
He has a strong personality.