Whence dwimmerlaik?

[Morthoron]

Evidently the Rohirrim are a superstitious lot, and anything beyond their ken would be looked at suspiciously as "sorcery" (whether good, bad or indifferent), hence dwimmerlaik (dweomerlayk) as a nethworldly/shadowy presence capable of spell-casting accords with that distrust.

One has only to review Éomer's wariness upon meeting Aragorn, Gimli and Legolas on the open plain and hearing of Lothlórien:

The Rider looked at them with renewed wonder, but his eyes hardened. ‘Then there is a Lady in the Golden Wood, as old tales tell!’ he said. ‘Few escape her nets, they say. These are strange days! But if you have her favour, then you also are net-weavers and sorcerers, maybe.’

"Net-weavers", "sorcerors" -- one could have easily wedged in dwimmerlaik as an additional synonym to that list of ill-omen.