wheat
麥 centers on wheat as a grain crop. Its meaning is straightforward: the plant and its edible seeds.
麥 is a pictograph of a wheat plant, with the top 來 originally depicting the ear of wheat and the lower part the roots or stalk. The modern form retains this plant-like shape.
The top 來 looks like a wheat ear with hanging grains, and the lower part resembles the stalk and roots. Together, 麥 is a wheat plant.
For バク, imagine a big sack of wheat: sack -> バク, and the sack is full of 麥.