Emily Dickinson Lexicon

WELK'IN, n. [Sax. wolc, wolcen, a cloud, the air, ether, the vault of heaven; G. wolke, a cloud. Qu. Sax. wealcan, to roll, to full.]

The visible regions of the air; the vault of heaven. – Chaucer. Milton. [This is obsolete, unless in poetry.] Welkin eye, in Shakspeare, is interpreted by Johnson, a blue eye, from welkin, the sky; by Todd, a rolling eye, from Sax. wealcan, to roll; and by Entick, a languishing eye. See Welk. It is obsolete, at least in New England.