The word for today is pigweed.

From the Greek word “amarantos” meaning … one that does not wither (never fading flower).

According to Webster’s:

Any of several coarse weeds from the Amaranth family, with dense and bristly clusters of small flowers.
Any of several goosefoots, especially lamb’s-quarters.

Other information:

The name stems from the fact that some of the weedy plants are supposedly used as pig fodder.

Amaranth seeds, similar to quinoa and buckwheat, are exceptionally high in protein yet free of the problematic ingredient known as gluten. Research indicates that amaranth seeds and their oil extract might benefit sufferers of hypertension, heart disease, high blood pressure, and high cholesterol while also offering the added benefit of having anti-oxidant qualities.

John Milton’s Paradise Lost
“Immortal amarant, a flower which once
In paradise, fast by the tree of life,
Began to bloom; but soon for man’s offence
To heaven removed, where first it grew, there grows”