No matter what one thinks the passer actually refers to (e.g. see this short analysis of Carmina II), pipiare (‘chirping’ or ‘peeping’ in the avian sense) does seem to be related to the whole concept of Twitter and ‘tweeting’, obviously. Accordingly, I chanced upon a nice page which conjugated pipiare in all its forms which offered a sort of ‘menu of potential terminology’ and initially was in a gerundive state of mind, and threw out the suggestion of Pipianda (things chirped) for Twitter, and pipiandum (a thing chirped) for a tweet. Other forms were suggested, most notably pipulum for Tweet, by Dave Oosterhuis (@VerbaLatina). Bill Thayer (@LacusCurtius) suggested ‘pipiatum‘ to save a character (we do tweet in a 140 character world, of course), which was also nice because it brought back the ‘t’ sound.