The Chitarrone was first mentioned in a report about a Medici marriage. In theis text both words "chitarrone" and "theorbo" were used simultaneus. This report was written in 1582. The fact for using theses two words for one instrument, for me is important in context of the use of the word theorbo in the baroque period. I will pic up this theme there.
The different existing chitarrone instruments have a great variety of string length. The "smaller" ones with about 76 cm are suitable for solo playing and the bigger or huge ones ( Tieffenbrucker, London ) are instruments only for continuo playing, as more than 90cm string length are too much for solo pieces.