Why the name?

(1) It is small (hence the "mini").
(2) It is a first intent of doing this (hence the "a"). In line with many other design decisions, xkcd 927 is applied - in order to avoid siding with those who defend starting to count in 0 and siding with those who defend starting to count in 1, start to count in 'a', which is without a trace of doubt the first letter of the English alphabet. Minia was started with a belief in the principle of this approach to dealing with irreconciliable adversaries. Tabs? spaces? here you will never have any of those forced down your throat.
(3) It is notably short, beating in length several beasts like Python, JavaScript, Haskell, Scheme, or Pascal; and in tie with some other beasts such as Swift or ALGOL.
(4) It seemed available for this use.
(5) The domain name was available.
(6) It means something. Check the Wikipedia.
(7) Hopefully it doesn't sound offensive in too many languages.

Keep asking!

To be continued...