It doesn't seem much like a shortener honestly - the domain is short, sure, but the urls it generates are quite long-ish [1]. A better way, in my opinion, would be to just use a single word, with up to ~3 retries before it adds another one to it. Is it open source? It would be quite neat to deploy on one of my domains ;)
[1] https://getrektby.us gets 'shortened' to http://trim.kim/ApologyPossibilityOccasionally