Xylo means wood. Metallo is metal.

+-------------------+-----------------------+--------------------+ | | Xylo(phone) | Metallophone | +-------------------+-----------------------+--------------------+ | Bars Only | Xylophone F4-C8 | Glockenspiel G5-C8 | | | Xylorimba C3-C8 | | | Bars + Resonators | Marimba (C2 to A2)-C7 | Vibraphone F3-F6 | +-------------------+-----------------------+--------------------+

Xylophone and metallophone may both signify their group of instruments (wooden or metal bars).

When you type "xylorimba" or "xylophone" in google image search, you'll see that they often like to sell them with resonators. Thus what really differentiates them is their range:

Xylophones have a range of two-and-a-half to four octaves.

have a range of two-and-a-half to four octaves. Marimbas have a larger range, usually between three and five octaves.

have a larger range, usually between three and five octaves. Xylorimba (sometimes referred to as xylo-marimba or marimba-xylophone) is a xylophone with an extended range downwards to include those pitches normally in the range of the marimba.

The written staff notes also differ from their actual pitch. E.g. for convenience Xylophone is written F3-C7, but it sounds an octave higher: F4-C8. Glockenspiel is written G3-C6, but sounds two octaves higher. (C4 is the "middle C", the sound/pitch that the middle C key of piano makes)