Sure: taxonomies.pl.
Usage is simple: feed it a bunch of filenames on STDIN, and it will add random taxonomies to their TOML front matter. So, to create 3 taxonomies with 1000 terms each, and then add 1-3 of them with 1-5 randomly-selected terms to each article:
find content -name '*.md' | taxonomies.pl -T 3 -t 1000 -m 5
The thousand content files that I generated with my wikiblog.sh script are here (5MB tarball). I just copied them repeatedly into different sections to increase the article count, and then ran the taxonomy-adder on the results.
-j