The above is very good and clear. My understanding was that monofilament mean't single strand, or a brush made up of single strands.
The flocked has a more colourfull derivation. Years ago itinerant pedlars would travel from town to town selling brushes and saucepans etc. Some of these pedlars were of Irish descent, and would often remark after a succesful days trading- There I just sold another of the Flockers-.
In this way it became the actual name for a type of brush.Very good for getting the dirt out of the corners missus.