Etymology

cp. OIcel mugga ‘mugginess, soft drizzling mist’, Icel mugga ‘snow (in fine weather)’ and a range of Scandinavian cognates (e.g. Norw mugge (masc.) ‘damp fog’, mugge (fem.) ‘humidity’, Shetl. mugg ‘drizzle’, etc.), and the derived Icel v. mugga ‘to snow (in fine weather)’. It is usual to derive the ME from the ON because of the lack of close analogues in WGmc. The Scandinavian words are usually referred to PIE *mug- or *muk- (as for mekely). The origin of ON -gg- is unclear, and has not been used as a test of loan.

PGmc Ancestor

*mug- 

Proposed ON Etymon (OIcel representative)

mugga ‘mugginess, soft drizzling mist’
(ONP mugga (2) (sb.))

Other Scandinavian Reflexes

Icel mugga, Norw mugg, mugge, ODan mu(g)en, Dan mug, Sw mugg 

OE Cognate

Phonological and morphological markers

Summary category

BB1c

Attestation

Only at Gaw 2080 in ME; occurs as n. and v. in MnE Sc., N and E dial (see EDD).

Occurrences in the Gersum Corpus

Gaw 2080

The (now standard) interpretation of the word as referring to light rain was first advanced by Wright 1906: 215; earlier works (incl. Bj. and Stratmann-Bradley) follow the Morris gloss ‘was cloudy’.  

Bibliography

MED mugen (v.) , OED3 mug (v.1) , HTOED , EDD mug (sb.2 and v.2), Dance muged, Bj. 250, de Vries mugga (1), Mag. mugga (1)