In the -system of general semantics, extensional enumerations frequently appear. As it is often impossible (by lack of space-time) to list them completely, it is necessary to use words like "etc.". It can mean, for example, that the enumeration which precedes is incomplete, that I am conscious of it, that the enumerated examples appear sufficient to me to understand what I intend, etc.
This extensional tool also points out the second premise (not all), helps us get rid of "either/or" formulations, etc.
Each time you use this word, try to consider at least one additional item of your enumeration, so that is not just a "way to speak".
Korzybski made such a heavy use of this word in Science and Sanity
that it was necessary to use a simplified notation:
The abreviation Stands for . , etc., , . ,etc. , ; etc.; . ? etc.? . : etc.: . ! etc.!