Glass Surname and variants

English and German: metonymic occupational name for a glazier or glass blower, from Old English glæs ‘glass’ (akin to Glad, referring originally to the bright shine of the material), Middle High German glas.
Irish and Scottish: Anglicized form of the epithet glas ‘gray’, ‘green’, ‘blue’ or any of various Gaelic surnames derived from it.
German: altered form of the personal name Klass, a reduced form of Nikolaus (see Nicholas).
Jewish (Ashkenazic): ornamental name from German Glass ‘glass’, or a metonymic occupational name for a glazier or glass blower.

Dictionary of American Family Names, Oxford University Press, ISBN 0-19-508137-4