köken: Uncertain. Proposals have been made connecting it with Proto-Indo-European *wegʷ- (“wet; moist”) (and thus Ancient Greek ὑγρός (hugrós) and Latin ūvidus), or with the Proto-Indo-European root behind Ancient Greek ἀδήν (adḗn) and Latin inguen.
köken: From Old Galician-Portuguese balorento (13ᵗʰ century, Cantigas de Santa Maria; attested as nickname, Balurentus, in a 12ᵗʰ Latin local document). From balor (“mould”) + -ento. Cognate with Portuguese bolorento.
The senses "smelly" and "grumpy" go back to different origins. The former pertains to Muff (“bad smell”) from Middle Low German muffen; the latter to Muffel (“grumpy person”), which is an Upper German dialect word of unknown origin. In contemporary German both senses often overlap (see below). It is therefore impossible to treat them as separate words anymore. Compare the same mixture of roots in…