small jade wine cup
斝 refers to a specific type of small jade wine cup, likely an ancient ritual vessel. Its meaning is narrow and object-specific.
The exact historical development of 斝 is uncertain. It likely combines 吅 (possibly representing mouths or a decorative element), 冖 (a cover), and 斗 (a ladle or measuring vessel), suggesting a covered vessel for liquids.
The top 吅 looks like two mouths, the middle 冖 is a lid, and the bottom 斗 is a ladle. Imagine a small jade cup with a lid, used to ladle wine for two people.
For カ, picture a car (カ) made of jade, tiny enough to hold wine: a jade car cup. Car -> カ.