Sources

Bog Alain, the Bog of Allan: Watson 1904, 137 [under headform of Allangrange which he gives as Alan (no article)]

There are a number of other names in this area containing the Allan element: Allangrange (Allangrang 1654 Blaeu map Moray), Allanglach, Allanrich and Bogallan. Watson implies this relates to a Pictish name in G Alan, gen. Alain, presumably a river-name of the burn now called Little Burn.