At this section of the British Library website you can locate titles for books published between 1473 and 1800. If the material was published in the UK or its possessions, Colonial America or any place else on the planet, and it was printed in English, it very well might be listed in this database.
Now short title does not refer to the length of the actual name of the book. As you can see from the example below, titles could be quiet descriptive:
My understanding is that it refers to limited or special publications produced quickly. I'm thinking like pamphlets, broadsheets and the early equivalents of instant publishing.
As you can see, you can view the records in a variety of formats such as a three line summary listing, full MARC tags, or which institution has the actual document.
This is a good resource if you are researching ephemeral publications that give a sense of time and place.
It is also valuable if you want to brush up on your MARC skills if it has been long time since you have sweated a MARC code. Check it out.