I wonder if Terry was thinking of the Indian caste system in his choice of the word 'sweeper' to indicate the lowly position of a sweeper.

from Wikipaedia

'The Bhangi are the segment of Indian society that were traditionally relegated to only the dirtiest and most unpleasant jobs. Even within the Dalits, the group once known as "Untouchables", Bhangis were considered to have the lowest status.

Although Bhangis are sometimes referred to as "sweepers", the word does not really convey the extraordinary conditions under which they generally work. Sweeping often involves crawling inside a tiny chamber underneath a so-called "dry toilet", removing the excrement, and carrying it away in a bucket on one's head.

Efforts have been made to improve sanitation systems in India, including laws that ban the construction of dry toilets. However Bhangis continue to work in their traditional roles and they continue to face considerable social barriers.'