出典:Wiktionary
From Middle English ithand, an alteration (due to assimilation to suffix -and) of ithen, from Old Norse iðinn (“assiduous, diligent”), from iðja, iðna (“to do, perform”), from ið (“a restless motion”), equivalent to ithe + -and and/or ithe + -en. Cognate with Icelandic iðinn (“diligent”), Norwegian idig (“busy”), Danish idelig (“continual”), and perhaps to English eddy.
ithand (comparative more ithand, superlative most ithand)