store up, station troops

屯 is a pictograph of a plant as it sprouts, with the seed coat still attached to the stem. Its original meaning is the initial growth of plants, but this sense was later taken over by the character 芚. Before a seed can germinate, it must accumulate strength in order to break through the seed coat and the soil and put forth leaves. Therefore, 屯 is nowadays used to mean to gather or assemble, and also to station troops.