Green’s Dictionary of Slang

constructed with the, low spirits, ‘the sulks’; thus mumpish adj., depressed, sulky.

1599		Nashe Praise of the Red Herring 45: The sunne was so in his mumps vppon it.
1689		Gazophylacium anglicanum n.p.: Momps [...] He hath the Mumps, (i. e.) he is angry, and silent with it.
c.1698		B.E. Dict. Canting Crew n.p.: mulligrubs or mumps a Counterfeit Fit of the Sullens.
1707		N. Ward ‘The Humours of a Coffee-House’ Writings (1704) 281: The Mumps take thee, for an old Dotard.
1725		New Canting Dict. [as cit. c.1698].
1754		B. Martin Eng. Dict. (2nd edn).
c.1840		‘Barbary Bell’ in Holloway & Black II (1979) 56: I sat in the mumps I could not tell how.
1873		Sl. Dict. 232: Mumps the miserables. To feel mumpish is to be heavy, dull, and stupid.
1887		W.E. Henley ‘Villon’s Good-Night’ in Farmer Musa Pedestris (1896) 175: And gave me mumps and mulligrubs / With skilly and swill that made me clam.
1895		C. Crowe Aus. Sl. Dict. 51: Mumps,‘the miserables,’ feeling wretchedly.
1896		G.F. Northall Warwickshire Word-Book 153: Mumps. The sulks; a sulky mood.