Past participle of 'undertake'; having started or agreed to do something.
From Old English 'under-' (beneath, among) combined with 'take' (to grasp). The meaning shifted from physically taking something under oneself to taking on responsibility or a task.
An undertaker (person who handles funerals) and an undertaking (a task) come from the same root—because funeral directors literally 'took under' themselves the responsibility of handling the dead, which was one of the most significant undertakings in a community.
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