c. 1400, schalowe "not deep," probably from or related to Old English sceald (see shoal (n.)). Of breathing, attested from 1875; of thought or feeling, "superficial," by 1580s. The noun, usually shallows, is first recorded 1570s, from the adjective.
a shallow cut
established a shallow beachhead
a shallow dish
hit the ball to shallow left field
a shallow closet
shallow water
in a shallow trance
shallow breathing
a night of shallow fretful sleep
shallow people
his arguments seemed shallow and tedious
The silt shallowed the canal
the lake shallowed over time
shaky
shale
shall
shallop
shallot
shallow
shalom
sham
shaman
shamanism
shamble