其

qi

it(s), his, her

the shape of a winnowing basket to sort grain (it) is leaning against a stand

土

tu

earth, dust, terra, soil

基

ji

base, foundation

winnowing basket/it/grain (qi) + soil (tu)

grains comes from the soil - the foundation

月

yue

moon, month

期

qi

period, phase

winnowing basket/it/grain (qi) + moon (yue)

certain grains for certain periods according to the moon  

旗

qi

flag

square [yan] + winnowing basket/it/grain (qi)

'it' - the square fluttering flag