Garden cress, botanically called Cardamine, a diminutive of the Greek kardamon, called in Latin nasturtium, sometimes called Nose-smart (Kara-damon, head-afflicting); so nasturtium is Nasi-tortium (nose-twisting), called so in consequence of its pungency.
When ladies' smocks of silver white Do paint the meadows with delight.
Called Ladies' smocks because the flowers resemble linen exposed to whiten on the grass- “when maidens bleach their summer smocks.” There is, however, a purple tint which mars its perfect whiteness. Another name of the plant is “Cuckoo-flower,” because it comes into flower when the cuckoo sings.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894