While we use collective nouns like "flock" for birds and "herd" for cattle, the concept of a "word swarm" is more figurative. It implies a rapid and overwhelming influx of words, which doesn't naturally lend itself to a single, specific noun.
You could use more descriptive phrases to convey the same idea:
* A torrent of words
* A deluge of language
* A flood of verbiage
* A cacophony of voices
Ultimately, the best choice will depend on the specific context and the desired effect.