The mandola came first. Well before the mandolin anyway.
A corruption of the word mandorla (almond in Italian) which describes its shape.
The common family is the Lute or al L'Ud - 'the wood' because the soundboard wasn't skin like a banjo. The Lute was introduced to Europe by the Moors.
The Mandola was a derivation of the Lute without the characteristic right-angle headstock. It is sometimes said that the Mandola was originally a simpler 'beginners' Lute. A later, smaller mandola was developed and became known as a mandolina, which led to the mandolin.
Traditional tuned a fifth below the mandolin, it mirrored the viola. In fact the two families had matching counterparts:
In more recent times, the Mandola is often seen re-tuned to the GDAE of mandolins, but an octave below. There is some controversy over whether the scale length or the tuning determines the instrument name, therefore, by scale length it is a Mandola - tuned to octave mandolin, or by tuning, it is a mandolin, but an octave lower. It is often used in traditional English and Irish music.
Fed up of the Mandola debate?
Here is the definitive word!
What is the instrument that is the shape and size of a mandola, maybe a tad longer, tuned GDAE an octave below a mandolin?
Is it an Octave Mandola? an Octave Mandolin?
Well, here are the facts, a suggestion and at the end of it all call it what you will but make sure the other person understands.
There were three violas, for the viola, by a different route, pre-dates the Mandola:
The Tenor tuning dropped out of popularity when the Viola family range was rationalised with the Violincello taking the higher register into the Tenor range. Previously it had only been the Bass instrument.
Given this, it appears that what we have is a re-emergence of a Tenor instrument of the Mandola family.
So, the Mandola is properly Alto, Treble, CGDA as it has always (mostly) been. The slightly longer, bigger instrument is a Tenor Mandola. I can feel waves of strong feeling now!
The Tenor Voice range is often given as C below middle C to G above which also sometimes leads people to apply 'Tenor' to the CGDA tuning - as in the Tenor Banjo (and Tenor Mandola unfortunately). This is incorrect. The CGDA tuned Banjo is actually in the Alto range, just as the Mandola is.
Correctly then, it's a Tenor Mandola, but it might be more correct to say it's simply a Mandola, tenor tuned rather than alto tuned.