Is there a reason to use extremely abbreviated table names?

We're using a database setup from a vendor's application that has horrifically hard to read database table names, and no documentation on what is stored where. I can see why one might want to obfuscate their table structure in a proprietary app, but one of the selling points of this application (Enterprise Resource Planning) was it's customizability. Table names are like aptrx (Accounts Payable Transactions) and apmaster_all (curiously, this is the vendors table). It's an extremely complex database, so I was wondering if there was any logic to the convention or if it was simply being obfuscated intentionally or otherwise. To the best of my knowledge the length of the table name won't affect performance noticeably, correct? The database is very complex (hundreds of tables) so sorting makes sense, but I can't imagine why AccountsPayableTransactions isn't preferable to aptrx....