aside from the obvious, that it's the American word for "glossary" (cf "Scatland"!), I presume you're referring to Kilmichael Glassary?

I would guess (and I should point out that I am only guessing) that the "Glassary" part comes from the Gaelic "glasraidh" meaning greens (as in green fields)

Cheers
Andy S

Megalithic sites of Perthshire
http://www.andysweet.co.uk/stones/

As a 'gloggy', my reference in this matter is always the - for ever on sale- booklet "Scottish Place Names" by George Mackay.
This is what is says:

Glassery (Argyll and Bute) 'Grey Shieling'. Glas (Scottish Gealic) 'grey'; airidh (Scottish Gealic) 'shieling'.

It's in line with BigSweetie's -not so rough- guess!

Cheers,

Jan

Same root as "glasgow", which I've heard translated as both "dear green place" and "blue-green hollows". Possibly where "glastonbury" is coming from too?

"glas: a lock, Irish, Old Irish glas: *glapsâ; English clasp.
glas: grey, Irish glas, green, pale, Early Irish glass, Welsh, Old Welsh, Breton glas, green: *glasto-, green; German glast, sheen (Bez.), root glas, to which German glass, English glass, are probably allied."
- MacBain's Etymological Irish Gaelic Dictionary

"glas: nf. g. glaise; d. glais; pl.+an, lock, fetter : glas-làmh, handcuff
glas: grey"
- MacFarlane's Scottish Gaelic Dictionary

"glass: green (of nature), verdant, soft, pale, pasty, ashen (colour), grey (of animal), raw, unfledged, sappy, callow (of youth); trigger, bond, iron; lock, stream"
- Kelly's Manx Dictionary