The prophet Amos once described himself as a "dresser of sycamores." What does the phrase mean?

It seems that the trees called 'sycamores' produced a small fruit of little taste. It was the fruit of the poor. To succeed in getting it even to that poor state someone had to puncture the skin of the fruit while on the tree. That's what the 'dresser' did.

A DRESSER OF SYCAMORES

The first classical prophet was not a professional preacher.
Amos labored as a migrant farm worker traveling throughout Israel to find employment.
Among his jobs was that of tending Sycamore trees.
These are not the European or North American variety, but a type of plant native to the Middle East.
Sometimes called “the poor man’s fig tree,” they produce a small fruit encased in a husk.
During the growing season these husks must be pierced with a sharp stick for the fruit to ripen.
The yield was of little value.
Despite his low-paying occupation, Amos was rich in prophecy.
He was the first prophet to write down his words.