There is no deceit in a brimmer.

A brimmer is a cup filled to the rim, making the amount served plain to see. The saying treats that visible fullness as proof that the drink has not been short-measured.

The point is the quantity in the cup rather than the honesty of anyone’s conversation. A serving that reaches the brim leaves no hidden shortfall.

Use it as a lighthearted remark when asking for a cup to be filled to the brim or when receiving one that has been filled that way. It draws attention to the plainly generous measure.