Small strings compression library

FWIW, no changes from when it came out 7 years ago. It was discussed here then on HN, at https://news.ycombinator.com/item?id=540048 , with 22 comments.

Another short string compressor is Shoco, discussed here a year ago at https://news.ycombinator.com/item?id=10060018 .

What's the algo? Is it just a static English letter frequency library for short strings? That's what it sounds like to me based on the description.