Coire Etchachan is a corrie at the head of Gleann Doire overlooking the upper end of the track leading towards Làirig Laoigh.
As a place name Coire Etchachan is obscure – the most likely derivations are 'of the juniper', and 'of the expansive place' – both are likely since there is a lot of dwarf juniper in the corrie, and together with the head of Gleann Doire it is a big open place.
There's also no reason why it can't be both - the people of Strath Spey using one name, while the people of Strath Dee the other. I can easily imagine drovers from the north (for example) travelling south through the narrowness of the Làirig Laoigh, and crossing the watershed into the head of Gleann Doire feeling themselves in an 'expansive place' - referring to the place as such. For the keepers of Mar (for example) travelling to the head of the glen, or through the corrie towards Ben Macdui - after the expansiveness of Gleann Doire, might only note the abundance of juniper - referring to the place as such.
Double place names, like I'm suggesting, aren't unknown in the Cairngorms, and it could be the case that the Gaelic for 'expansive place' - Éiteachan, and 'of the juniper' - Aitionnach are such sound-alikes to non-Gaelic speakers that no one realised the corrie had two names, which were both garbled for long enough that now Gaelic speakers cannot confidently disentangle a meaning from Coire Etchachan.