二甲基胂酸

• 二(number two; two horizontal strokes)ASSOCIATIVE

Two parallel horizontal strokes symbolize the number two.

• 甲(turtle shell; carapace)ASSOCIATIVE

The character depicts a turtle's shell with a crack running through it, symbolizing the hard protective covering.

• 酉(wine vessel; ferment)RADICAL
• 夋(slow manner; leisurely pace)PHONETIC

Fermenting alcohol produces sourness, which is exactly the character for sour.