ill-

From Old Swedish ill- (“evil”). Attested since end of the 13th century. Related to illa.

ill-

1. evil

   ‎ill- + ‎vilja (“will”) → ‎illvilja (“ill-will”)

2. Generic amplifier

   ‎ill- + ‎grön (“green”) → ‎illgrön (“very green”)

   ‎ill- + ‎tjut (“shriek; howl”) → ‎illtjut (“loud shriek”)

• “ill-”, in Svenska Akademiens ordlista [Wordlist of the Swedish Academy] (in Swedish)
• “ill-”, in Svensk ordbok [Dictionary of Swedish] (in Swedish)