This is what I found:

Where first word is

a genus of grasshoppers, commonly called bird grasshoppers, many of which swarm as locusts

and second one is

the act or habit of describing or regarding something as unimportant, of having no value or being worthless

Some explaination about each stanza:

The Egyptians died as they could not hide, 
When the famine flies and the plant life dies.

One of the ten plagues Yahweh inflicted upon Egypt, according to the biblical Book of Exodus, was locusts.

In seventy four there appeared some more.
Even clothes some wore they had ate and tore.

In 1874 Rocky Mountain locust caused $200 million in crop damage in Colorado, Kansas, Minnesota, Missouri, Nebraska, and other states. One farmer reported that the locusts seemed "like a great white cloud, like a snowstorm, blocking out the sun like vapor". The locusts ate not only the grass and valuable crops, but also leather, wood, sheep's wool, and in extreme cases, even clothes off peoples' backs". [source: Wikipedia]

The first is unique and it's from old Greek.

The first word indicates a genus of grasshoppers, and etymologically it has greek origin.

Now the second bit doesn't help a whit.
You'd better stop it as the act's not fit.
To estimate it is a bad habit.
You had best be quit is my solemn writ.

As already said, the second word indicates the act or habit of describing or regarding something as unimportant, of having no value or being worthless; so it's "a bad habit" you'd better avoid.

The second complete in a lingual feat.

According to Wiktionary, the second word word was inspired by a line in the Eton Latin Grammar that gave a rule for certain verbs that take an object in the genitive case: “flocci, nauci, nihilī, pilī, assis, huius, teruncii, hīs verbīs, aestimō, pendō, faciō, pecūliāriter adduntur”.1 This translates loosely to: “The verbs aestimo, pendo and facio when used in the sense of ‘to value’ or ‘to care’ irregularly take the following objects in the genitive case: flocci, nauci, nihilī, pilī, assis (“penny”), huius (“this”) and teruncii (“farthing”)”.

It's also often cited as the longest non-technical word in the English language, being one letter longer than the commonly cited antidisestablishmentarianism.

This is what I found:

Where first word is

a genus of grasshoppers, commonly called bird grasshoppers, many of which swarm as locusts

and second one is

the act or habit of describing or regarding something as unimportant, of having no value or being worthless

Some explaination about each stanza:

The Egyptians died as they could not hide, 
When the famine flies and the plant life dies.

One of the ten plagues Yahweh inflicted upon Egypt, according to the biblical Book of Exodus, was locusts. One significant note on the genus of locust chosen: National Geographic published an article about a locust infestation in Egypt of the same genus in 2013.

In seventy four there appeared some more.
Even clothes some wore they had ate and tore.

In 1874 Rocky Mountain locust caused $200 million in crop damage in Colorado, Kansas, Minnesota, Missouri, Nebraska, and other states. One farmer reported that the locusts seemed "like a great white cloud, like a snowstorm, blocking out the sun like vapor". The locusts ate not only the grass and valuable crops, but also leather, wood, sheep's wool, and in extreme cases, even clothes off peoples' backs". [source: Wikipedia]

The first is unique and it's from old Greek.

The first word indicates a genus of grasshoppers, and etymologically it has greek origin.

Now the second bit doesn't help a whit.
You'd better stop it as the act's not fit.
To estimate it is a bad habit.
You had best be quit is my solemn writ.

As already said, the second word indicates the act or habit of describing or regarding something as unimportant, of having no value or being worthless; so it's "a bad habit" you'd better avoid.

The second complete in a lingual feat.

According to Wiktionary, the second word word was inspired by a line in the Eton Latin Grammar that gave a rule for certain verbs that take an object in the genitive case: “flocci, nauci, nihilī, pilī, assis, huius, teruncii, hīs verbīs, aestimō, pendō, faciō, pecūliāriter adduntur”.1 This translates loosely to: “The verbs aestimo, pendo and facio when used in the sense of ‘to value’ or ‘to care’ irregularly take the following objects in the genitive case: flocci, nauci, nihilī, pilī, assis (“penny”), huius (“this”) and teruncii (“farthing”)”.

It's also often cited as the longest non-technical word in the English language, being one letter longer than the commonly cited antidisestablishmentarianism.

This is what I found:

Where first word is

a genus of grasshoppers, commonly called bird grasshoppers, many of which swarm as locusts

and second one is

the act or habit of describing or regarding something as unimportant, of having no value or being worthless

This is what I found:

Where first word is

a genus of grasshoppers, commonly called bird grasshoppers, many of which swarm as locusts

and second one is

the act or habit of describing or regarding something as unimportant, of having no value or being worthless

Some explaination about each stanza:

The Egyptians died as they could not hide, 
When the famine flies and the plant life dies.

One of the ten plagues Yahweh inflicted upon Egypt, according to the biblical Book of Exodus, was locusts.

In seventy four there appeared some more.
Even clothes some wore they had ate and tore.

In 1874 Rocky Mountain locust caused $200 million in crop damage in Colorado, Kansas, Minnesota, Missouri, Nebraska, and other states. One farmer reported that the locusts seemed "like a great white cloud, like a snowstorm, blocking out the sun like vapor". The locusts ate not only the grass and valuable crops, but also leather, wood, sheep's wool, and in extreme cases, even clothes off peoples' backs". [source: Wikipedia]

The first is unique and it's from old Greek.

The first word indicates a genus of grasshoppers, and etymologically it has greek origin.

Now the second bit doesn't help a whit.
You'd better stop it as the act's not fit.
To estimate it is a bad habit.
You had best be quit is my solemn writ.

As already said, the second word indicates the act or habit of describing or regarding something as unimportant, of having no value or being worthless; so it's "a bad habit" you'd better avoid.

The second complete in a lingual feat.

According to Wiktionary, the second word word was inspired by a line in the Eton Latin Grammar that gave a rule for certain verbs that take an object in the genitive case: “flocci, nauci, nihilī, pilī, assis, huius, teruncii, hīs verbīs, aestimō, pendō, faciō, pecūliāriter adduntur”.1 This translates loosely to: “The verbs aestimo, pendo and facio when used in the sense of ‘to value’ or ‘to care’ irregularly take the following objects in the genitive case: flocci, nauci, nihilī, pilī, assis (“penny”), huius (“this”) and teruncii (“farthing”)”.

It's also often cited as the longest non-technical word in the English language, being one letter longer than the commonly cited antidisestablishmentarianism.